diff --git a/build.gradle b/build.gradle
index c13c146..7d28c4c 100644
--- a/build.gradle
+++ b/build.gradle
@@ -82,6 +82,7 @@ dependencies {
     implementation 'io.springfox:springfox-swagger-ui:2.9.2'
     implementation 'com.github.javafaker:javafaker:1.0.2'
     implementation 'com.fasterxml.jackson.dataformat:jackson-dataformat-csv:2.10.3'
+    implementation 'com.fasterxml.jackson.datatype:jackson-datatype-jsr310:2.10.3'
 
     compileOnly 'org.projectlombok:lombok'
     annotationProcessor 'org.projectlombok:lombok'
diff --git a/mysql/db/entrypoint/schema.sql b/mysql/db/entrypoint/schema.sql
index 2b059c6..a97d31e 100644
--- a/mysql/db/entrypoint/schema.sql
+++ b/mysql/db/entrypoint/schema.sql
@@ -1,15 +1,15 @@
 CREATE TABLE event
 (
-    event_id INT PRIMARY KEY AUTO_INCREMENT,
-    group_id VARCHAR(36) NOT NULL,
-    user_id VARCHAR(50),
-    event_type VARCHAR(36),
+    event_id      INT PRIMARY KEY AUTO_INCREMENT,
+    group_id      VARCHAR(36) NOT NULL,
+    user_id       VARCHAR(50) NOT NULL,
+    event_type    VARCHAR(32) NOT NULL,
     event_payload JSON
 );
 
 CREATE TABLE invite
 (
-    invite_id INT PRIMARY KEY AUTO_INCREMENT,
-    group_id VARCHAR(36) NOT NULL,
+    invite_id   INT PRIMARY KEY AUTO_INCREMENT,
+    group_id    VARCHAR(36) NOT NULL,
     invite_link VARCHAR(36) NOT NULL
 );
diff --git a/src/main/java/mops/gruppen2/aspect/LogAspect.java b/src/main/java/mops/gruppen2/aspect/LogAspect.java
index 64a3a13..bad5b06 100644
--- a/src/main/java/mops/gruppen2/aspect/LogAspect.java
+++ b/src/main/java/mops/gruppen2/aspect/LogAspect.java
@@ -13,7 +13,7 @@ import org.springframework.context.annotation.Profile;
 import org.springframework.stereotype.Component;
 
 @Log4j2
-@Profile("dev")
+@Profile({"dev", "docker"})
 @Aspect
 @Component
 public class LogAspect {
@@ -36,12 +36,12 @@ public class LogAspect {
 
 
     @Before("@annotation(mops.gruppen2.aspect.annotation.Trace)")
-    public void logCustom(JoinPoint joinPoint) {
+    public static void logCustom(JoinPoint joinPoint) {
         log.trace(((MethodSignature) joinPoint.getSignature()).getMethod().getAnnotation(Trace.class).value());
     }
 
     @Before("@annotation(mops.gruppen2.aspect.annotation.TraceMethodCall) || logMethodCalls()")
-    public void logMethodCall(JoinPoint joinPoint) {
+    public static void logMethodCall(JoinPoint joinPoint) {
         log.trace("Methodenaufruf: {} ({})",
                   joinPoint.getSignature().getName(),
                   joinPoint.getSourceLocation().getWithinType().getName().replace("mops.gruppen2.", ""));
@@ -50,7 +50,7 @@ public class LogAspect {
     }
 
     @Around("@annotation(mops.gruppen2.aspect.annotation.TraceExecutionTime)")
-    public Object logExecutionTime(ProceedingJoinPoint joinPoint) throws Throwable {
+    public static Object logExecutionTime(ProceedingJoinPoint joinPoint) throws Throwable {
         long start = System.currentTimeMillis();
         joinPoint.proceed();
         long stop = System.currentTimeMillis();
diff --git a/src/main/java/mops/gruppen2/config/WebConfig.java b/src/main/java/mops/gruppen2/config/WebConfig.java
new file mode 100644
index 0000000..ab5607e
--- /dev/null
+++ b/src/main/java/mops/gruppen2/config/WebConfig.java
@@ -0,0 +1,15 @@
+package mops.gruppen2.config;
+
+import mops.gruppen2.config.converter.StringToLimitConverter;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.format.FormatterRegistry;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+
+@Configuration
+public class WebConfig implements WebMvcConfigurer {
+
+    @Override
+    public void addFormatters(FormatterRegistry registry) {
+        registry.addConverter(new StringToLimitConverter());
+    }
+}
diff --git a/src/main/java/mops/gruppen2/config/converter/StringToLimitConverter.java b/src/main/java/mops/gruppen2/config/converter/StringToLimitConverter.java
new file mode 100644
index 0000000..bd12c49
--- /dev/null
+++ b/src/main/java/mops/gruppen2/config/converter/StringToLimitConverter.java
@@ -0,0 +1,12 @@
+package mops.gruppen2.config.converter;
+
+import mops.gruppen2.domain.model.group.wrapper.Limit;
+import org.springframework.core.convert.converter.Converter;
+
+public class StringToLimitConverter implements Converter<String, Limit> {
+
+    @Override
+    public Limit convert(String value) {
+        return new Limit(Long.parseLong(value));
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/AddMemberEvent.java b/src/main/java/mops/gruppen2/domain/event/AddMemberEvent.java
new file mode 100644
index 0000000..f492037
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/event/AddMemberEvent.java
@@ -0,0 +1,44 @@
+package mops.gruppen2.domain.event;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AllArgsConstructor;
+import lombok.Value;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.GroupFullException;
+import mops.gruppen2.domain.exception.IdMismatchException;
+import mops.gruppen2.domain.exception.UserAlreadyExistsException;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.User;
+
+/**
+ * Fügt einen einzelnen Nutzer einer Gruppe hinzu.
+ */
+@Log4j2
+@Value
+@AllArgsConstructor
+public class AddMemberEvent extends Event {
+
+    @JsonProperty("user")
+    User user;
+
+    public AddMemberEvent(Group group, String exec, String target, User user) throws IdMismatchException {
+        super(group.getId(), exec, target);
+        this.user = user;
+
+        if (!target.equals(user.getId())) {
+            throw new IdMismatchException("Der User passt nicht zur angegebenen userid.");
+        }
+    }
+
+    @Override
+    protected void applyEvent(Group group) throws UserAlreadyExistsException, GroupFullException {
+        group.addMember(target, user);
+
+        log.trace("\t\t\t\t\tNeue Members: {}", group.getMembers());
+    }
+
+    @Override
+    public String getType() {
+        return EventType.ADDMEMBER.toString();
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/AddUserEvent.java b/src/main/java/mops/gruppen2/domain/event/AddUserEvent.java
deleted file mode 100644
index ce2d766..0000000
--- a/src/main/java/mops/gruppen2/domain/event/AddUserEvent.java
+++ /dev/null
@@ -1,49 +0,0 @@
-package mops.gruppen2.domain.event;
-
-import com.fasterxml.jackson.annotation.JsonProperty;
-import lombok.AllArgsConstructor;
-import lombok.Value;
-import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.exception.EventException;
-import mops.gruppen2.domain.helper.ValidationHelper;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Role;
-import mops.gruppen2.domain.model.User;
-
-/**
- * Fügt einen einzelnen Nutzer einer Gruppe hinzu.
- */
-
-@Log4j2
-@Value
-@AllArgsConstructor
-public class AddUserEvent extends Event {
-
-    @JsonProperty("givenname")
-    String givenname;
-
-    @JsonProperty("familyname")
-    String familyname;
-
-    @JsonProperty("email")
-    String email;
-
-    public AddUserEvent(Group group, User user) {
-        super(group.getGroupid(), user.getUserid());
-        givenname = user.getGivenname();
-        familyname = user.getFamilyname();
-        email = user.getEmail();
-    }
-
-    @Override
-    protected void applyEvent(Group group) throws EventException {
-        ValidationHelper.throwIfMember(group, new User(userid));
-        ValidationHelper.throwIfGroupFull(group);
-
-        group.getMembers().put(userid, new User(userid, givenname, familyname, email));
-        group.getRoles().put(userid, Role.MEMBER);
-
-        log.trace("\t\t\t\t\tNeue Members: {}", group.getMembers());
-        log.trace("\t\t\t\t\tNeue Rollen: {}", group.getRoles());
-    }
-}
diff --git a/src/main/java/mops/gruppen2/domain/event/CreateGroupEvent.java b/src/main/java/mops/gruppen2/domain/event/CreateGroupEvent.java
index ac381d9..0d763e7 100644
--- a/src/main/java/mops/gruppen2/domain/event/CreateGroupEvent.java
+++ b/src/main/java/mops/gruppen2/domain/event/CreateGroupEvent.java
@@ -4,10 +4,10 @@ import com.fasterxml.jackson.annotation.JsonProperty;
 import lombok.AllArgsConstructor;
 import lombok.Value;
 import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Type;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.exception.BadArgumentException;
+import mops.gruppen2.domain.model.group.Group;
 
+import java.time.LocalDateTime;
 import java.util.UUID;
 
 @Log4j2
@@ -15,24 +15,30 @@ import java.util.UUID;
 @AllArgsConstructor// Value generiert den allArgsConstrucot nur, wenn keiner explizit angegeben ist
 public class CreateGroupEvent extends Event {
 
-    @JsonProperty("parent")
-    UUID parent;
+    @JsonProperty("date")
+    LocalDateTime date;
 
-    @JsonProperty("type")
-    Type type;
-
-    public CreateGroupEvent(UUID groupId, User user, UUID parent, Type type) {
-        super(groupId, user.getUserid());
-        this.parent = parent;
-        this.type = type;
+    public CreateGroupEvent(UUID groupId, String exec, LocalDateTime date) {
+        super(groupId, exec, null);
+        this.date = date;
     }
 
     @Override
-    protected void applyEvent(Group group) {
-        group.setGroupid(groupid);
-        group.setParent(parent);
-        group.setType(type);
+    protected void applyEvent(Group group) throws BadArgumentException {
+        group.setId(groupid);
+        group.setCreator(exec);
+        group.setCreationDate(date);
 
         log.trace("\t\t\t\t\tNeue Gruppe: {}", group.toString());
     }
+
+    @Override
+    public String getType() {
+        return EventType.CREATEGROUP.toString();
+    }
+
+    @Override
+    public String toString() {
+        return "(" + version + "," + groupid + "," + date + ")";
+    }
 }
diff --git a/src/main/java/mops/gruppen2/domain/event/DeleteGroupEvent.java b/src/main/java/mops/gruppen2/domain/event/DeleteGroupEvent.java
deleted file mode 100644
index a2f79be..0000000
--- a/src/main/java/mops/gruppen2/domain/event/DeleteGroupEvent.java
+++ /dev/null
@@ -1,30 +0,0 @@
-package mops.gruppen2.domain.event;
-
-import lombok.AllArgsConstructor;
-import lombok.Value;
-import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.User;
-
-@Log4j2
-@Value
-@AllArgsConstructor
-public class DeleteGroupEvent extends Event {
-
-    public DeleteGroupEvent(Group group, User user) {
-        super(group.getGroupid(), user.getUserid());
-    }
-
-    @Override
-    protected void applyEvent(Group group) {
-        group.getRoles().clear();
-        group.getMembers().clear();
-        group.setTitle(null);
-        group.setDescription(null);
-        group.setType(null);
-        group.setParent(null);
-        group.setLimit(null);
-
-        log.trace("\t\t\t\t\tGelöschte Gruppe: {}", group);
-    }
-}
diff --git a/src/main/java/mops/gruppen2/domain/event/DeleteUserEvent.java b/src/main/java/mops/gruppen2/domain/event/DeleteUserEvent.java
deleted file mode 100644
index eb7d3fe..0000000
--- a/src/main/java/mops/gruppen2/domain/event/DeleteUserEvent.java
+++ /dev/null
@@ -1,33 +0,0 @@
-package mops.gruppen2.domain.event;
-
-import lombok.AllArgsConstructor;
-import lombok.Value;
-import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.exception.EventException;
-import mops.gruppen2.domain.helper.ValidationHelper;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.User;
-
-/**
- * Entfernt ein einzelnes Mitglied einer Gruppe.
- */
-@Log4j2
-@Value
-@AllArgsConstructor
-public class DeleteUserEvent extends Event {
-
-    public DeleteUserEvent(Group group, User user) {
-        super(group.getGroupid(), user.getUserid());
-    }
-
-    @Override
-    protected void applyEvent(Group group) throws EventException {
-        ValidationHelper.throwIfNoMember(group, new User(userid));
-
-        group.getMembers().remove(userid);
-        group.getRoles().remove(userid);
-
-        log.trace("\t\t\t\t\tNeue Members: {}", group.getMembers());
-        log.trace("\t\t\t\t\tNeue Rollen: {}", group.getRoles());
-    }
-}
diff --git a/src/main/java/mops/gruppen2/domain/event/DestroyGroupEvent.java b/src/main/java/mops/gruppen2/domain/event/DestroyGroupEvent.java
new file mode 100644
index 0000000..78a1b45
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/event/DestroyGroupEvent.java
@@ -0,0 +1,29 @@
+package mops.gruppen2.domain.event;
+
+import lombok.AllArgsConstructor;
+import lombok.Value;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.NoAccessException;
+import mops.gruppen2.domain.model.group.Group;
+
+@Log4j2
+@Value
+@AllArgsConstructor
+public class DestroyGroupEvent extends Event {
+
+    public DestroyGroupEvent(Group group, String exec) {
+        super(group.getId(), exec, null);
+    }
+
+    @Override
+    protected void applyEvent(Group group) throws NoAccessException {
+        group.destroy(exec);
+
+        log.trace("\t\t\t\t\tGelöschte Gruppe: {}", group.toString());
+    }
+
+    @Override
+    public String getType() {
+        return EventType.DESTROYGROUP.toString();
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/Event.java b/src/main/java/mops/gruppen2/domain/event/Event.java
index 3fbf498..be97a44 100644
--- a/src/main/java/mops/gruppen2/domain/event/Event.java
+++ b/src/main/java/mops/gruppen2/domain/event/Event.java
@@ -1,59 +1,92 @@
 package mops.gruppen2.domain.event;
 
+import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonSubTypes;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
-import lombok.AllArgsConstructor;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.BadArgumentException;
 import mops.gruppen2.domain.exception.EventException;
-import mops.gruppen2.domain.exception.GroupIdMismatchException;
-import mops.gruppen2.domain.model.Group;
+import mops.gruppen2.domain.exception.IdMismatchException;
+import mops.gruppen2.domain.model.group.Group;
 
 import java.util.UUID;
 
 @Log4j2
-@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type")
-@JsonSubTypes({@JsonSubTypes.Type(value = AddUserEvent.class, name = "AddUserEvent"),
-               @JsonSubTypes.Type(value = CreateGroupEvent.class, name = "CreateGroupEvent"),
-               @JsonSubTypes.Type(value = DeleteUserEvent.class, name = "DeleteUserEvent"),
-               @JsonSubTypes.Type(value = UpdateGroupDescriptionEvent.class, name = "UpdateGroupDescriptionEvent"),
-               @JsonSubTypes.Type(value = UpdateGroupTitleEvent.class, name = "UpdateGroupTitleEvent"),
-               @JsonSubTypes.Type(value = UpdateRoleEvent.class, name = "UpdateRoleEvent"),
-               @JsonSubTypes.Type(value = DeleteGroupEvent.class, name = "DeleteGroupEvent"),
-               @JsonSubTypes.Type(value = UpdateUserLimitEvent.class, name = "UpdateUserLimitEvent")})
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "class")
+@JsonSubTypes({@JsonSubTypes.Type(value = AddMemberEvent.class, name = "ADDMEMBER"),
+               @JsonSubTypes.Type(value = CreateGroupEvent.class, name = "CREATEGROUP"),
+               @JsonSubTypes.Type(value = DestroyGroupEvent.class, name = "DESTROYGROUP"),
+               @JsonSubTypes.Type(value = KickMemberEvent.class, name = "KICKMEMBER"),
+               @JsonSubTypes.Type(value = SetDescriptionEvent.class, name = "SETDESCRIPTION"),
+               @JsonSubTypes.Type(value = SetInviteLinkEvent.class, name = "SETLINK"),
+               @JsonSubTypes.Type(value = SetLimitEvent.class, name = "SETLIMIT"),
+               @JsonSubTypes.Type(value = SetParentEvent.class, name = "SETPARENT"),
+               @JsonSubTypes.Type(value = SetTitleEvent.class, name = "SETTITLE"),
+               @JsonSubTypes.Type(value = SetTypeEvent.class, name = "SETTYPE"),
+               @JsonSubTypes.Type(value = UpdateRoleEvent.class, name = "UPDATEROLE")})
 @Getter
-@AllArgsConstructor
 @NoArgsConstructor // Lombok needs a default constructor in the base class
 public abstract class Event {
 
+
     @JsonProperty("groupid")
     protected UUID groupid;
 
-    @JsonProperty("userid")
-    protected String userid;
+    @JsonProperty("version")
+    protected long version;
+
+    @JsonProperty("exec")
+    protected String exec;
+
+    @JsonProperty("target")
+    protected String target;
+
+    public Event(UUID groupid, String exec, String target) {
+        this.groupid = groupid;
+        this.exec = exec;
+        this.target = target;
+    }
+
+    public void init(long version) {
+        if (this.version != 0) {
+            throw new BadArgumentException("Event wurde schon initialisiert. (" + getType() + ")");
+        }
+
+        log.trace("Event wurde initialisiert. (" + getType() + "," + version + ")");
+
+        this.version = version;
+    }
 
     public Group apply(Group group) throws EventException {
-        checkGroupIdMatch(group.getGroupid());
+        log.trace("Event wird angewendet:\t{}", this);
 
-        log.trace("Event angewendet:\t{}", this);
+        if (version == 0) {
+            throw new BadArgumentException("Event wurde nicht initialisiert.");
+        }
 
+        checkGroupIdMatch(group.getId());
+        group.update(version);
         applyEvent(group);
 
         return group;
     }
 
-    private void checkGroupIdMatch(UUID groupId) {
+    private void checkGroupIdMatch(UUID groupId) throws IdMismatchException {
         // CreateGroupEvents müssen die Id erst initialisieren
         if (this instanceof CreateGroupEvent) {
             return;
         }
 
         if (!groupid.equals(groupId)) {
-            throw new GroupIdMismatchException(getClass().toString());
+            throw new IdMismatchException("Das Event gehört zu einer anderen Gruppe");
         }
     }
 
     protected abstract void applyEvent(Group group) throws EventException;
+
+    @JsonIgnore
+    public abstract String getType();
 }
diff --git a/src/main/java/mops/gruppen2/domain/event/EventType.java b/src/main/java/mops/gruppen2/domain/event/EventType.java
new file mode 100644
index 0000000..a444326
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/event/EventType.java
@@ -0,0 +1,15 @@
+package mops.gruppen2.domain.event;
+
+public enum EventType {
+    ADDMEMBER,
+    CREATEGROUP,
+    DESTROYGROUP,
+    KICKMEMBER,
+    SETDESCRIPTION,
+    SETLINK,
+    SETLIMIT,
+    SETPARENT,
+    SETTITLE,
+    SETTYPE,
+    UPDATEROLE
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/KickMemberEvent.java b/src/main/java/mops/gruppen2/domain/event/KickMemberEvent.java
new file mode 100644
index 0000000..cc3ad27
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/event/KickMemberEvent.java
@@ -0,0 +1,33 @@
+package mops.gruppen2.domain.event;
+
+import lombok.AllArgsConstructor;
+import lombok.Value;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.LastAdminException;
+import mops.gruppen2.domain.exception.UserNotFoundException;
+import mops.gruppen2.domain.model.group.Group;
+
+/**
+ * Entfernt ein einzelnes Mitglied einer Gruppe.
+ */
+@Log4j2
+@Value
+@AllArgsConstructor
+public class KickMemberEvent extends Event {
+
+    public KickMemberEvent(Group group, String exec, String target) {
+        super(group.getId(), exec, target);
+    }
+
+    @Override
+    protected void applyEvent(Group group) throws UserNotFoundException, LastAdminException {
+        group.kickMember(target);
+
+        log.trace("\t\t\t\t\tNeue Members: {}", group.getMembers());
+    }
+
+    @Override
+    public String getType() {
+        return EventType.KICKMEMBER.toString();
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/SetDescriptionEvent.java b/src/main/java/mops/gruppen2/domain/event/SetDescriptionEvent.java
new file mode 100644
index 0000000..976dedd
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/event/SetDescriptionEvent.java
@@ -0,0 +1,40 @@
+package mops.gruppen2.domain.event;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AllArgsConstructor;
+import lombok.Value;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.NoAccessException;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.wrapper.Description;
+
+import javax.validation.Valid;
+
+/**
+ * Ändert nur die Gruppenbeschreibung.
+ */
+@Log4j2
+@Value
+@AllArgsConstructor
+public class SetDescriptionEvent extends Event {
+
+    @JsonProperty("desc")
+    Description description;
+
+    public SetDescriptionEvent(Group group, String exec, @Valid Description description) {
+        super(group.getId(), exec, null);
+        this.description = description;
+    }
+
+    @Override
+    protected void applyEvent(Group group) throws NoAccessException {
+        group.setDescription(exec, description);
+
+        log.trace("\t\t\t\t\tNeue Beschreibung: {}", group.getDescription());
+    }
+
+    @Override
+    public String getType() {
+        return EventType.SETDESCRIPTION.toString();
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/SetInviteLinkEvent.java b/src/main/java/mops/gruppen2/domain/event/SetInviteLinkEvent.java
new file mode 100644
index 0000000..25f2af0
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/event/SetInviteLinkEvent.java
@@ -0,0 +1,37 @@
+package mops.gruppen2.domain.event;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AllArgsConstructor;
+import lombok.Value;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.NoAccessException;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.wrapper.Link;
+
+import javax.validation.Valid;
+
+@Log4j2
+@Value
+@AllArgsConstructor
+public class SetInviteLinkEvent extends Event {
+
+    @JsonProperty("link")
+    Link link;
+
+    public SetInviteLinkEvent(Group group, String exec, @Valid Link link) {
+        super(group.getId(), exec, null);
+        this.link = link;
+    }
+
+    @Override
+    protected void applyEvent(Group group) throws NoAccessException {
+        group.setLink(exec, link);
+
+        log.trace("\t\t\t\t\tNeuer Link: {}", group.getLink());
+    }
+
+    @Override
+    public String getType() {
+        return EventType.SETLINK.toString();
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/SetLimitEvent.java b/src/main/java/mops/gruppen2/domain/event/SetLimitEvent.java
new file mode 100644
index 0000000..d160435
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/event/SetLimitEvent.java
@@ -0,0 +1,38 @@
+package mops.gruppen2.domain.event;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AllArgsConstructor;
+import lombok.Value;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.BadArgumentException;
+import mops.gruppen2.domain.exception.NoAccessException;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.wrapper.Limit;
+
+import javax.validation.Valid;
+
+@Log4j2
+@Value
+@AllArgsConstructor
+public class SetLimitEvent extends Event {
+
+    @JsonProperty("limit")
+    Limit limit;
+
+    public SetLimitEvent(Group group, String exec, @Valid Limit limit) {
+        super(group.getId(), exec, null);
+        this.limit = limit;
+    }
+
+    @Override
+    protected void applyEvent(Group group) throws BadArgumentException, NoAccessException {
+        group.setLimit(exec, limit);
+
+        log.trace("\t\t\t\t\tNeues UserLimit: {}", group.getLimit());
+    }
+
+    @Override
+    public String getType() {
+        return EventType.SETLIMIT.toString();
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/SetParentEvent.java b/src/main/java/mops/gruppen2/domain/event/SetParentEvent.java
new file mode 100644
index 0000000..736cc89
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/event/SetParentEvent.java
@@ -0,0 +1,37 @@
+package mops.gruppen2.domain.event;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AllArgsConstructor;
+import lombok.Value;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.NoAccessException;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.wrapper.Parent;
+
+import javax.validation.Valid;
+
+@Log4j2
+@Value
+@AllArgsConstructor
+public class SetParentEvent extends Event {
+
+    @JsonProperty("parent")
+    Parent parent;
+
+    public SetParentEvent(Group group, String exec, @Valid Parent parent) {
+        super(group.getId(), exec, null);
+        this.parent = parent;
+    }
+
+    @Override
+    protected void applyEvent(Group group) throws NoAccessException {
+        group.setParent(exec, parent);
+
+        log.trace("\t\t\t\t\tNeues Parent: {}", group.getParent());
+    }
+
+    @Override
+    public String getType() {
+        return EventType.SETPARENT.toString();
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/SetTitleEvent.java b/src/main/java/mops/gruppen2/domain/event/SetTitleEvent.java
new file mode 100644
index 0000000..17e6599
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/event/SetTitleEvent.java
@@ -0,0 +1,41 @@
+package mops.gruppen2.domain.event;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AllArgsConstructor;
+import lombok.Value;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.NoAccessException;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.wrapper.Title;
+
+import javax.validation.Valid;
+
+/**
+ * Ändert nur den Gruppentitel.
+ */
+@Log4j2
+@Value
+@AllArgsConstructor
+public class SetTitleEvent extends Event {
+
+    @JsonProperty("title")
+    Title title;
+
+    public SetTitleEvent(Group group, String exec, @Valid Title title) {
+        super(group.getId(), exec, null);
+        this.title = title;
+    }
+
+    @Override
+    protected void applyEvent(Group group) throws NoAccessException {
+        group.setTitle(exec, title);
+
+        log.trace("\t\t\t\t\tNeuer Titel: {}", group.getTitle());
+    }
+
+    @Override
+    public String getType() {
+        return EventType.SETTITLE.toString();
+    }
+
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/SetTypeEvent.java b/src/main/java/mops/gruppen2/domain/event/SetTypeEvent.java
new file mode 100644
index 0000000..e87c8ee
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/event/SetTypeEvent.java
@@ -0,0 +1,36 @@
+package mops.gruppen2.domain.event;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AllArgsConstructor;
+import lombok.Value;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.EventException;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Type;
+
+import javax.validation.Valid;
+
+@Log4j2
+@Value
+@AllArgsConstructor
+public class SetTypeEvent extends Event {
+
+    @JsonProperty("type")
+    Type type;
+
+    public SetTypeEvent(Group group, String exec, @Valid Type type) {
+        super(group.getId(), exec, null);
+
+        this.type = type;
+    }
+
+    @Override
+    protected void applyEvent(Group group) throws EventException {
+        group.setType(exec, type);
+    }
+
+    @Override
+    public String getType() {
+        return EventType.SETTYPE.toString();
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/event/UpdateGroupDescriptionEvent.java b/src/main/java/mops/gruppen2/domain/event/UpdateGroupDescriptionEvent.java
deleted file mode 100644
index b5d5dc4..0000000
--- a/src/main/java/mops/gruppen2/domain/event/UpdateGroupDescriptionEvent.java
+++ /dev/null
@@ -1,33 +0,0 @@
-package mops.gruppen2.domain.event;
-
-import com.fasterxml.jackson.annotation.JsonProperty;
-import lombok.AllArgsConstructor;
-import lombok.Value;
-import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.model.Description;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.User;
-
-/**
- * Ändert nur die Gruppenbeschreibung.
- */
-@Log4j2
-@Value
-@AllArgsConstructor
-public class UpdateGroupDescriptionEvent extends Event {
-
-    @JsonProperty("desc")
-    Description description;
-
-    public UpdateGroupDescriptionEvent(Group group, User user, Description description) {
-        super(group.getGroupid(), user.getUserid());
-        this.description = description;
-    }
-
-    @Override
-    protected void applyEvent(Group group) {
-        group.setDescription(description);
-
-        log.trace("\t\t\t\t\tNeue Beschreibung: {}", group.getDescription());
-    }
-}
diff --git a/src/main/java/mops/gruppen2/domain/event/UpdateGroupTitleEvent.java b/src/main/java/mops/gruppen2/domain/event/UpdateGroupTitleEvent.java
deleted file mode 100644
index 96e469f..0000000
--- a/src/main/java/mops/gruppen2/domain/event/UpdateGroupTitleEvent.java
+++ /dev/null
@@ -1,34 +0,0 @@
-package mops.gruppen2.domain.event;
-
-import com.fasterxml.jackson.annotation.JsonProperty;
-import lombok.AllArgsConstructor;
-import lombok.Value;
-import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Title;
-import mops.gruppen2.domain.model.User;
-
-/**
- * Ändert nur den Gruppentitel.
- */
-@Log4j2
-@Value
-@AllArgsConstructor
-public class UpdateGroupTitleEvent extends Event {
-
-    @JsonProperty("title")
-    Title title;
-
-    public UpdateGroupTitleEvent(Group group, User user, Title title) {
-        super(group.getGroupid(), user.getUserid());
-        this.title = title;
-    }
-
-    @Override
-    protected void applyEvent(Group group) {
-        group.setTitle(title);
-
-        log.trace("\t\t\t\t\tNeuer Titel: {}", group.getTitle());
-    }
-
-}
diff --git a/src/main/java/mops/gruppen2/domain/event/UpdateRoleEvent.java b/src/main/java/mops/gruppen2/domain/event/UpdateRoleEvent.java
index 48d0b3c..0164d51 100644
--- a/src/main/java/mops/gruppen2/domain/event/UpdateRoleEvent.java
+++ b/src/main/java/mops/gruppen2/domain/event/UpdateRoleEvent.java
@@ -4,11 +4,10 @@ import com.fasterxml.jackson.annotation.JsonProperty;
 import lombok.AllArgsConstructor;
 import lombok.Value;
 import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.LastAdminException;
 import mops.gruppen2.domain.exception.UserNotFoundException;
-import mops.gruppen2.domain.helper.ValidationHelper;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Role;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Role;
 
 /**
  * Aktualisiert die Gruppenrolle eines Teilnehmers.
@@ -21,18 +20,21 @@ public class UpdateRoleEvent extends Event {
     @JsonProperty("role")
     Role role;
 
-    public UpdateRoleEvent(Group group, User user, Role tole) {
-        super(group.getGroupid(), user.getUserid());
-        role = tole;
+    public UpdateRoleEvent(Group group, String exec, String target, Role role) {
+        super(group.getId(), exec, target);
+        this.role = role;
     }
 
     @Override
-    protected void applyEvent(Group group) throws UserNotFoundException {
-        ValidationHelper.throwIfNoMember(group, new User(userid));
+    protected void applyEvent(Group group) throws UserNotFoundException, LastAdminException {
+        group.memberPutRole(target, role);
 
-        group.getRoles().put(userid, role);
+        log.trace("\t\t\t\t\tNeue Admin: {}", group.getAdmins());
+    }
 
-        log.trace("\t\t\t\t\tNeue Rollen: {}", group.getRoles());
+    @Override
+    public String getType() {
+        return EventType.UPDATEROLE.toString();
     }
 
 }
diff --git a/src/main/java/mops/gruppen2/domain/event/UpdateUserLimitEvent.java b/src/main/java/mops/gruppen2/domain/event/UpdateUserLimitEvent.java
deleted file mode 100644
index f3fdd56..0000000
--- a/src/main/java/mops/gruppen2/domain/event/UpdateUserLimitEvent.java
+++ /dev/null
@@ -1,36 +0,0 @@
-package mops.gruppen2.domain.event;
-
-import com.fasterxml.jackson.annotation.JsonProperty;
-import lombok.AllArgsConstructor;
-import lombok.Value;
-import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.exception.BadParameterException;
-import mops.gruppen2.domain.exception.EventException;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Limit;
-import mops.gruppen2.domain.model.User;
-
-@Log4j2
-@Value
-@AllArgsConstructor
-public class UpdateUserLimitEvent extends Event {
-
-    @JsonProperty("limit")
-    Limit limit;
-
-    public UpdateUserLimitEvent(Group group, User user, Limit limit) {
-        super(group.getGroupid(), user.getUserid());
-        this.limit = limit;
-    }
-
-    @Override
-    protected void applyEvent(Group group) throws EventException {
-        if (limit.getUserLimit() < group.getMembers().size()) {
-            throw new BadParameterException("Teilnehmerlimit zu klein.");
-        }
-
-        group.setLimit(limit);
-
-        log.trace("\t\t\t\t\tNeues UserLimit: {}", group.getLimit());
-    }
-}
diff --git a/src/main/java/mops/gruppen2/domain/exception/BadArgumentException.java b/src/main/java/mops/gruppen2/domain/exception/BadArgumentException.java
new file mode 100644
index 0000000..425a6d1
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/exception/BadArgumentException.java
@@ -0,0 +1,12 @@
+package mops.gruppen2.domain.exception;
+
+import org.springframework.http.HttpStatus;
+
+public class BadArgumentException extends EventException {
+
+    private static final long serialVersionUID = -6757742013238625595L;
+
+    public BadArgumentException(String info) {
+        super(HttpStatus.BAD_REQUEST, "Fehlerhafter Parameter.", info);
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/exception/BadParameterException.java b/src/main/java/mops/gruppen2/domain/exception/BadParameterException.java
deleted file mode 100644
index 0d41a10..0000000
--- a/src/main/java/mops/gruppen2/domain/exception/BadParameterException.java
+++ /dev/null
@@ -1,12 +0,0 @@
-package mops.gruppen2.domain.exception;
-
-import org.springframework.http.HttpStatus;
-
-public class BadParameterException extends EventException {
-
-    private static final long serialVersionUID = -6757742013238625595L;
-
-    public BadParameterException(String info) {
-        super(HttpStatus.BAD_REQUEST, "Fehlerhafter Parameter angegeben!", info);
-    }
-}
diff --git a/src/main/java/mops/gruppen2/domain/exception/BadPayloadException.java b/src/main/java/mops/gruppen2/domain/exception/BadPayloadException.java
index fcd1d0f..4281ac2 100644
--- a/src/main/java/mops/gruppen2/domain/exception/BadPayloadException.java
+++ b/src/main/java/mops/gruppen2/domain/exception/BadPayloadException.java
@@ -7,7 +7,7 @@ public class BadPayloadException extends EventException {
     private static final long serialVersionUID = -3978242017847155629L;
 
     public BadPayloadException(String info) {
-        super(HttpStatus.INTERNAL_SERVER_ERROR, "Die Payload konnte nicht übersetzt werden!", info);
+        super(HttpStatus.INTERNAL_SERVER_ERROR, "Payload konnte nicht übersetzt werden.", info);
     }
 }
 
diff --git a/src/main/java/mops/gruppen2/domain/exception/GroupFullException.java b/src/main/java/mops/gruppen2/domain/exception/GroupFullException.java
index 53bf3bc..5f2d4c6 100644
--- a/src/main/java/mops/gruppen2/domain/exception/GroupFullException.java
+++ b/src/main/java/mops/gruppen2/domain/exception/GroupFullException.java
@@ -7,7 +7,7 @@ public class GroupFullException extends EventException {
     private static final long serialVersionUID = -4011141160467668713L;
 
     public GroupFullException(String info) {
-        super(HttpStatus.INTERNAL_SERVER_ERROR, "Die Gruppe hat die maximale Mitgliederanzahl bereits erreicht!", info);
+        super(HttpStatus.INTERNAL_SERVER_ERROR, "Gruppe hat maximale Teilnehmeranzahl bereits erreicht.", info);
     }
 }
 
diff --git a/src/main/java/mops/gruppen2/domain/exception/GroupIdMismatchException.java b/src/main/java/mops/gruppen2/domain/exception/GroupIdMismatchException.java
deleted file mode 100644
index d762f87..0000000
--- a/src/main/java/mops/gruppen2/domain/exception/GroupIdMismatchException.java
+++ /dev/null
@@ -1,13 +0,0 @@
-package mops.gruppen2.domain.exception;
-
-import org.springframework.http.HttpStatus;
-
-public class GroupIdMismatchException extends EventException {
-
-    private static final long serialVersionUID = 7944077617758922089L;
-
-    public GroupIdMismatchException(String info) {
-        super(HttpStatus.INTERNAL_SERVER_ERROR, "Falsche Gruppe für Event.", info);
-    }
-}
-
diff --git a/src/main/java/mops/gruppen2/domain/exception/GroupNotFoundException.java b/src/main/java/mops/gruppen2/domain/exception/GroupNotFoundException.java
index 86bcb0f..5a10585 100644
--- a/src/main/java/mops/gruppen2/domain/exception/GroupNotFoundException.java
+++ b/src/main/java/mops/gruppen2/domain/exception/GroupNotFoundException.java
@@ -7,7 +7,7 @@ public class GroupNotFoundException extends EventException {
     private static final long serialVersionUID = -4738218416842951106L;
 
     public GroupNotFoundException(String info) {
-        super(HttpStatus.NOT_FOUND, "Die Gruppe existiert nicht oder wurde gelöscht.", info);
+        super(HttpStatus.NOT_FOUND, "Gruppe existiert nicht oder wurde gelöscht.", info);
     }
 }
 
diff --git a/src/main/java/mops/gruppen2/domain/exception/IdMismatchException.java b/src/main/java/mops/gruppen2/domain/exception/IdMismatchException.java
new file mode 100644
index 0000000..1200f8b
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/exception/IdMismatchException.java
@@ -0,0 +1,13 @@
+package mops.gruppen2.domain.exception;
+
+import org.springframework.http.HttpStatus;
+
+public class IdMismatchException extends EventException {
+
+    private static final long serialVersionUID = 7944077617758922089L;
+
+    public IdMismatchException(String info) {
+        super(HttpStatus.INTERNAL_SERVER_ERROR, "Ids stimmen nicht überein.", info);
+    }
+}
+
diff --git a/src/main/java/mops/gruppen2/domain/exception/InvalidInviteException.java b/src/main/java/mops/gruppen2/domain/exception/InvalidInviteException.java
index a0f74b3..2f9b19e 100644
--- a/src/main/java/mops/gruppen2/domain/exception/InvalidInviteException.java
+++ b/src/main/java/mops/gruppen2/domain/exception/InvalidInviteException.java
@@ -7,7 +7,7 @@ public class InvalidInviteException extends EventException {
     private static final long serialVersionUID = 2643001101459427944L;
 
     public InvalidInviteException(String info) {
-        super(HttpStatus.NOT_FOUND, "Der Einladungslink ist ungültig oder die Gruppe wurde gelöscht.", info);
+        super(HttpStatus.NOT_FOUND, "Einladungslink ist ungültig oder Gruppe wurde gelöscht.", info);
     }
 }
 
diff --git a/src/main/java/mops/gruppen2/domain/exception/LastAdminException.java b/src/main/java/mops/gruppen2/domain/exception/LastAdminException.java
new file mode 100644
index 0000000..a6af0ea
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/exception/LastAdminException.java
@@ -0,0 +1,12 @@
+package mops.gruppen2.domain.exception;
+
+import org.springframework.http.HttpStatus;
+
+public class LastAdminException extends EventException {
+
+    private static final long serialVersionUID = 9059481382346544288L;
+
+    public LastAdminException(String info) {
+        super(HttpStatus.INTERNAL_SERVER_ERROR, "Gruppe braucht mindestens einen Admin.", info);
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/exception/NoAccessException.java b/src/main/java/mops/gruppen2/domain/exception/NoAccessException.java
index 292f42f..27c569b 100644
--- a/src/main/java/mops/gruppen2/domain/exception/NoAccessException.java
+++ b/src/main/java/mops/gruppen2/domain/exception/NoAccessException.java
@@ -7,7 +7,7 @@ public class NoAccessException extends EventException {
     private static final long serialVersionUID = 1696988497122834654L;
 
     public NoAccessException(String info) {
-        super(HttpStatus.FORBIDDEN, "Hier hast du keinen Zugriff.", info);
+        super(HttpStatus.FORBIDDEN, "Kein Zugriff.", info);
     }
 }
 
diff --git a/src/main/java/mops/gruppen2/domain/exception/NoAdminAfterActionException.java b/src/main/java/mops/gruppen2/domain/exception/NoAdminAfterActionException.java
deleted file mode 100644
index 07a2afb..0000000
--- a/src/main/java/mops/gruppen2/domain/exception/NoAdminAfterActionException.java
+++ /dev/null
@@ -1,12 +0,0 @@
-package mops.gruppen2.domain.exception;
-
-import org.springframework.http.HttpStatus;
-
-public class NoAdminAfterActionException extends EventException {
-
-    private static final long serialVersionUID = 9059481382346544288L;
-
-    public NoAdminAfterActionException(String info) {
-        super(HttpStatus.INTERNAL_SERVER_ERROR, "Die Gruppe braucht einen Admin.", info);
-    }
-}
diff --git a/src/main/java/mops/gruppen2/domain/exception/PageNotFoundException.java b/src/main/java/mops/gruppen2/domain/exception/PageNotFoundException.java
index a54d2e6..0871621 100644
--- a/src/main/java/mops/gruppen2/domain/exception/PageNotFoundException.java
+++ b/src/main/java/mops/gruppen2/domain/exception/PageNotFoundException.java
@@ -7,7 +7,7 @@ public class PageNotFoundException extends EventException {
     private static final long serialVersionUID = 2374509005158710104L;
 
     public PageNotFoundException(String info) {
-        super(HttpStatus.NOT_FOUND, "Die Seite wurde nicht gefunden!", info);
+        super(HttpStatus.NOT_FOUND, "Seite wurde nicht gefunden.", info);
     }
 }
 
diff --git a/src/main/java/mops/gruppen2/domain/exception/UserAlreadyExistsException.java b/src/main/java/mops/gruppen2/domain/exception/UserAlreadyExistsException.java
index bb1d338..d0288cd 100644
--- a/src/main/java/mops/gruppen2/domain/exception/UserAlreadyExistsException.java
+++ b/src/main/java/mops/gruppen2/domain/exception/UserAlreadyExistsException.java
@@ -7,7 +7,7 @@ public class UserAlreadyExistsException extends EventException {
     private static final long serialVersionUID = -8150634358760194625L;
 
     public UserAlreadyExistsException(String info) {
-        super(HttpStatus.INTERNAL_SERVER_ERROR, "Der User existiert bereits.", info);
+        super(HttpStatus.INTERNAL_SERVER_ERROR, "User existiert bereits.", info);
     }
 }
 
diff --git a/src/main/java/mops/gruppen2/domain/exception/UserNotFoundException.java b/src/main/java/mops/gruppen2/domain/exception/UserNotFoundException.java
index 43c90e9..e1273df 100644
--- a/src/main/java/mops/gruppen2/domain/exception/UserNotFoundException.java
+++ b/src/main/java/mops/gruppen2/domain/exception/UserNotFoundException.java
@@ -7,7 +7,7 @@ public class UserNotFoundException extends EventException {
     private static final long serialVersionUID = 8347442921199785291L;
 
     public UserNotFoundException(String info) {
-        super(HttpStatus.NOT_FOUND, "Der User existiert nicht.", info);
+        super(HttpStatus.NOT_FOUND, "User existiert nicht.", info);
     }
 }
 
diff --git a/src/main/java/mops/gruppen2/domain/exception/WrongFileException.java b/src/main/java/mops/gruppen2/domain/exception/WrongFileException.java
index 63dbee6..45fcaa7 100644
--- a/src/main/java/mops/gruppen2/domain/exception/WrongFileException.java
+++ b/src/main/java/mops/gruppen2/domain/exception/WrongFileException.java
@@ -7,7 +7,7 @@ public class WrongFileException extends EventException {
     private static final long serialVersionUID = -166192514348555116L;
 
     public WrongFileException(String info) {
-        super(HttpStatus.BAD_REQUEST, "Die Datei ist keine valide CSV-Datei!", info);
+        super(HttpStatus.BAD_REQUEST, "Datei ist keine valide CSV-Datei.", info);
     }
 }
 
diff --git a/src/main/java/mops/gruppen2/domain/helper/APIHelper.java b/src/main/java/mops/gruppen2/domain/helper/APIHelper.java
index 5e7d04f..5da7990 100644
--- a/src/main/java/mops/gruppen2/domain/helper/APIHelper.java
+++ b/src/main/java/mops/gruppen2/domain/helper/APIHelper.java
@@ -1,16 +1,18 @@
 package mops.gruppen2.domain.helper;
 
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
 import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.model.Group;
+import mops.gruppen2.domain.model.group.Group;
 import mops.gruppen2.web.api.GroupRequestWrapper;
 
 import java.util.List;
 
+//TODO: sinnvolles format
 @Log4j2
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
 public final class APIHelper {
 
-    private APIHelper() {}
-
     public static GroupRequestWrapper wrap(long status, List<Group> groupList) {
         return new GroupRequestWrapper(status, groupList);
     }
diff --git a/src/main/java/mops/gruppen2/domain/helper/CommonHelper.java b/src/main/java/mops/gruppen2/domain/helper/CommonHelper.java
new file mode 100644
index 0000000..ce01dc7
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/helper/CommonHelper.java
@@ -0,0 +1,35 @@
+package mops.gruppen2.domain.helper;
+
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.event.EventType;
+
+import java.util.List;
+import java.util.UUID;
+import java.util.stream.Collectors;
+
+@Log4j2
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
+public final class CommonHelper {
+
+    public static String[] eventTypesToString(EventType... types) {
+        String[] stringtypes = new String[types.length];
+
+        for (int i = 0; i < types.length; i++) {
+            stringtypes[i] = types[i].toString();
+        }
+
+        return stringtypes;
+    }
+
+    public static List<String> uuidsToString(List<UUID> ids) {
+        return ids.stream()
+                  .map(UUID::toString)
+                  .collect(Collectors.toList());
+    }
+
+    public static boolean uuidIsEmpty(UUID uuid) {
+        return "00000000-0000-0000-0000-000000000000".equals(uuid.toString());
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/helper/CsvHelper.java b/src/main/java/mops/gruppen2/domain/helper/CsvHelper.java
index 3af7920..5a43b85 100644
--- a/src/main/java/mops/gruppen2/domain/helper/CsvHelper.java
+++ b/src/main/java/mops/gruppen2/domain/helper/CsvHelper.java
@@ -3,10 +3,12 @@ package mops.gruppen2.domain.helper;
 import com.fasterxml.jackson.databind.ObjectReader;
 import com.fasterxml.jackson.dataformat.csv.CsvMapper;
 import com.fasterxml.jackson.dataformat.csv.CsvSchema;
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
 import lombok.extern.log4j.Log4j2;
 import mops.gruppen2.domain.exception.EventException;
 import mops.gruppen2.domain.exception.WrongFileException;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.model.group.User;
 import org.springframework.web.multipart.MultipartFile;
 
 import java.io.IOException;
@@ -16,10 +18,9 @@ import java.util.List;
 import java.util.stream.Collectors;
 
 @Log4j2
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
 public final class CsvHelper {
 
-    private CsvHelper() {}
-
     public static List<User> readCsvFile(MultipartFile file) throws EventException {
         if (file == null || file.isEmpty()) {
             return Collections.emptyList();
diff --git a/src/main/java/mops/gruppen2/domain/helper/IdHelper.java b/src/main/java/mops/gruppen2/domain/helper/IdHelper.java
deleted file mode 100644
index e8e4f32..0000000
--- a/src/main/java/mops/gruppen2/domain/helper/IdHelper.java
+++ /dev/null
@@ -1,49 +0,0 @@
-package mops.gruppen2.domain.helper;
-
-import lombok.extern.log4j.Log4j2;
-
-import java.util.List;
-import java.util.UUID;
-import java.util.stream.Collectors;
-
-@Log4j2
-public final class IdHelper {
-
-    private IdHelper() {}
-
-    public static List<UUID> stringsToUUID(List<String> groupIds) {
-        return groupIds.stream()
-                       .map(IdHelper::stringToUUID)
-                       .collect(Collectors.toList());
-    }
-
-    /**
-     * Wandelt einen String in eine UUID um.
-     * Dabei wird eine "leere" UUID generiert, falls der String leer ist.
-     *
-     * @param groupId Id als String
-     *
-     * @return Id als UUID
-     */
-    public static UUID stringToUUID(String groupId) {
-        return groupId.isEmpty() ? emptyUUID() : UUID.fromString(groupId);
-    }
-
-    public static List<String> uuidsToString(List<UUID> groupIds) {
-        return groupIds.stream()
-                       .map(UUID::toString)
-                       .collect(Collectors.toList());
-    }
-
-    public static String uuidToString(UUID groupId) {
-        return groupId.toString();
-    }
-
-    public static boolean isEmpty(UUID id) {
-        return id == null || emptyUUID().equals(id);
-    }
-
-    public static UUID emptyUUID() {
-        return UUID.fromString("00000000-0000-0000-0000-000000000000");
-    }
-}
diff --git a/src/main/java/mops/gruppen2/domain/helper/JsonHelper.java b/src/main/java/mops/gruppen2/domain/helper/JsonHelper.java
index 93ea49b..614e929 100644
--- a/src/main/java/mops/gruppen2/domain/helper/JsonHelper.java
+++ b/src/main/java/mops/gruppen2/domain/helper/JsonHelper.java
@@ -2,6 +2,9 @@ package mops.gruppen2.domain.helper;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
 import lombok.extern.log4j.Log4j2;
 import mops.gruppen2.domain.event.Event;
 
@@ -9,10 +12,9 @@ import mops.gruppen2.domain.event.Event;
  * Übersetzt JSON-Event-Payloads zu Java-Event-Repräsentationen und zurück.
  */
 @Log4j2
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
 public final class JsonHelper {
 
-    private JsonHelper() {}
-
     /**
      * Übersetzt eine Java-Event-Repräsentation zu einem JSON-Event-Payload.
      *
@@ -24,7 +26,7 @@ public final class JsonHelper {
      */
 
     public static String serializeEvent(Event event) throws JsonProcessingException {
-        ObjectMapper mapper = new ObjectMapper();
+        ObjectMapper mapper = new ObjectMapper().registerModule(new JavaTimeModule());
         String payload = mapper.writeValueAsString(event);
         log.trace(payload);
         return payload;
@@ -40,7 +42,9 @@ public final class JsonHelper {
      * @throws JsonProcessingException Bei JSON Fehler
      */
     public static Event deserializeEvent(String json) throws JsonProcessingException {
-        ObjectMapper mapper = new ObjectMapper();
-        return mapper.readValue(json, Event.class);
+        ObjectMapper mapper = new ObjectMapper().registerModule(new JavaTimeModule());
+        Event event = mapper.readValue(json, Event.class);
+        log.trace(event);
+        return event;
     }
 }
diff --git a/src/main/java/mops/gruppen2/domain/helper/ValidationHelper.java b/src/main/java/mops/gruppen2/domain/helper/ValidationHelper.java
index 98e17ee..02cdc2e 100644
--- a/src/main/java/mops/gruppen2/domain/helper/ValidationHelper.java
+++ b/src/main/java/mops/gruppen2/domain/helper/ValidationHelper.java
@@ -1,118 +1,105 @@
 package mops.gruppen2.domain.helper;
 
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
 import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.exception.BadParameterException;
+import mops.gruppen2.domain.exception.BadArgumentException;
 import mops.gruppen2.domain.exception.GroupFullException;
+import mops.gruppen2.domain.exception.LastAdminException;
 import mops.gruppen2.domain.exception.NoAccessException;
-import mops.gruppen2.domain.exception.NoAdminAfterActionException;
 import mops.gruppen2.domain.exception.UserAlreadyExistsException;
 import mops.gruppen2.domain.exception.UserNotFoundException;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Type;
-import mops.gruppen2.domain.model.User;
-import mops.gruppen2.web.form.CreateForm;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Type;
 import org.keycloak.adapters.springsecurity.token.KeycloakAuthenticationToken;
 
-import static mops.gruppen2.domain.model.Role.ADMIN;
-
 @Log4j2
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
 public final class ValidationHelper {
 
-    private ValidationHelper() {}
-
-
-    // ######################################## CHECK ############################################
-
-
     /**
      * Überprüft, ob ein User in einer Gruppe teilnimmt.
      */
-    public static boolean checkIfMember(Group group, User user) {
-        return group.getMembers().containsKey(user.getUserid());
+    public static boolean checkIfMember(Group group, String userid) {
+        return group.isMember(userid);
     }
 
-    public static boolean checkIfLastMember(User user, Group group) {
-        return checkIfMember(group, user) && group.getMembers().size() == 1;
+    public static boolean checkIfLastMember(Group group, String userid) {
+        return checkIfMember(group, userid) && group.size() == 1;
     }
 
     /**
      * Überprüft, ob eine Gruppe voll ist.
      */
     public static boolean checkIfGroupFull(Group group) {
-        return group.getMembers().size() >= group.getLimit().getUserLimit();
+        return group.isFull();
     }
 
     /**
      * Überprüft, ob eine Gruppe leer ist.
      */
     public static boolean checkIfGroupEmpty(Group group) {
-        return group.getMembers().isEmpty();
+        return group.isEmpty();
     }
 
     /**
      * Überprüft, ob ein User in einer Gruppe Admin ist.
      */
-    public static boolean checkIfAdmin(Group group, User user) {
-        if (checkIfMember(group, user)) {
-            return group.getRoles().get(user.getUserid()) == ADMIN;
+    public static boolean checkIfAdmin(Group group, String userid) {
+        if (checkIfMember(group, userid)) {
+            return group.isAdmin(userid);
         }
         return false;
     }
 
-    public static boolean checkIfLastAdmin(User user, Group group) {
-        return checkIfAdmin(group, user) && group.getRoles().values().stream()
-                                                 .filter(role -> role == ADMIN)
-                                                 .count() == 1;
+    public static boolean checkIfLastAdmin(Group group, String userid) {
+        return checkIfAdmin(group, userid) && group.getAdmins().size() == 1;
     }
 
 
     // ######################################## THROW ############################################
 
 
-    public static void throwIfMember(Group group, User user) {
-        if (checkIfMember(group, user)) {
-            log.error("Benutzer {} ist schon in Gruppe {}", user, group);
-            throw new UserAlreadyExistsException(user.toString());
+    public static void throwIfMember(Group group, String userid) throws UserAlreadyExistsException {
+        if (checkIfMember(group, userid)) {
+            log.error("Benutzer {} ist schon in Gruppe {}", userid, group);
+            throw new UserAlreadyExistsException(userid);
         }
     }
 
-    public static void throwIfNoMember(Group group, User user) {
-        if (!checkIfMember(group, user)) {
-            log.error("Benutzer {} ist nicht in Gruppe {}!", user, group);
-            throw new UserNotFoundException(user.toString());
+    public static void throwIfNoMember(Group group, String userid) throws UserNotFoundException {
+        if (!checkIfMember(group, userid)) {
+            log.error("Benutzer {} ist nicht in Gruppe {}!", userid, group);
+            throw new UserNotFoundException(userid);
         }
     }
 
-    public static void throwIfNoAdmin(Group group, User user) {
-        if (!checkIfAdmin(group, user)) {
-            log.error("User {} ist kein Admin in Gruppe {}!", user, group);
-            throw new NoAccessException(group.toString());
+    public static void throwIfNoAdmin(Group group, String userid) throws NoAccessException {
+        if (!checkIfAdmin(group, userid)) {
+            log.error("User {} ist kein Admin in Gruppe {}!", userid, group);
+            throw new NoAccessException(group.getId().toString());
         }
     }
 
     /**
      * Schmeißt keine Exception, wenn der User der letzte User ist.
      */
-    public static void throwIfLastAdmin(User user, Group group) {
-        if (!checkIfLastMember(user, group) && checkIfLastAdmin(user, group)) {
-            throw new NoAdminAfterActionException("Du bist letzter Admin!");
+    public static void throwIfLastAdmin(Group group, String userid) throws LastAdminException {
+        if (!checkIfLastMember(group, userid) && checkIfLastAdmin(group, userid)) {
+            throw new LastAdminException("Du bist letzter Admin!");
         }
     }
 
-    public static void throwIfGroupFull(Group group) {
+    public static void throwIfGroupFull(Group group) throws GroupFullException {
         if (checkIfGroupFull(group)) {
             log.error("Die Gruppe {} ist voll!", group);
-            throw new GroupFullException(group.toString());
+            throw new GroupFullException(group.getId().toString());
         }
     }
 
-
-    // ##################################### VALIDATE FIELDS #####################################
-
-    public static void validateCreateForm(KeycloakAuthenticationToken token, CreateForm form) {
-        if (!token.getAccount().getRoles().contains("orga")
-            && form.getType() == Type.LECTURE) {
-            throw new BadParameterException("Eine Veranstaltung kann nur von ORGA erstellt werden.");
+    public static void validateCreateForm(KeycloakAuthenticationToken token, Type type) {
+        if (!token.getAccount().getRoles().contains("orga") && type == Type.LECTURE) {
+            throw new BadArgumentException("Nur Orga kann Veranstaltungen erstellen.");
         }
     }
 }
diff --git a/src/main/java/mops/gruppen2/domain/model/Group.java b/src/main/java/mops/gruppen2/domain/model/Group.java
deleted file mode 100644
index bd84a2d..0000000
--- a/src/main/java/mops/gruppen2/domain/model/Group.java
+++ /dev/null
@@ -1,39 +0,0 @@
-package mops.gruppen2.domain.model;
-
-import lombok.EqualsAndHashCode;
-import lombok.Getter;
-import lombok.Setter;
-import lombok.ToString;
-
-import java.util.HashMap;
-import java.util.Map;
-import java.util.UUID;
-
-/**
- * Repräsentiert den aggregierten Zustand einer Gruppe.
- */
-@Getter
-@Setter
-@EqualsAndHashCode(onlyExplicitlyIncluded = true)
-@ToString
-public class Group {
-
-    @EqualsAndHashCode.Include
-    private UUID groupid;
-
-    @ToString.Exclude
-    private UUID parent;
-
-    private Type type;
-
-    private Title title;
-    private Description description;
-
-    @ToString.Exclude
-    private Limit limit = new Limit(1); // Add initial user
-
-    @ToString.Exclude
-    private final Map<String, User> members = new HashMap<>();
-    @ToString.Exclude
-    private final Map<String, Role> roles = new HashMap<>();
-}
diff --git a/src/main/java/mops/gruppen2/domain/model/Role.java b/src/main/java/mops/gruppen2/domain/model/Role.java
deleted file mode 100644
index 1b66370..0000000
--- a/src/main/java/mops/gruppen2/domain/model/Role.java
+++ /dev/null
@@ -1,10 +0,0 @@
-package mops.gruppen2.domain.model;
-
-public enum Role {
-    ADMIN,
-    MEMBER;
-
-    public Role toggle() {
-        return this == ADMIN ? MEMBER : ADMIN;
-    }
-}
diff --git a/src/main/java/mops/gruppen2/domain/model/group/Group.java b/src/main/java/mops/gruppen2/domain/model/group/Group.java
new file mode 100644
index 0000000..bdd1fba
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/model/group/Group.java
@@ -0,0 +1,293 @@
+package mops.gruppen2.domain.model.group;
+
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+import lombok.ToString;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.BadArgumentException;
+import mops.gruppen2.domain.exception.GroupFullException;
+import mops.gruppen2.domain.exception.IdMismatchException;
+import mops.gruppen2.domain.exception.LastAdminException;
+import mops.gruppen2.domain.exception.NoAccessException;
+import mops.gruppen2.domain.exception.UserAlreadyExistsException;
+import mops.gruppen2.domain.exception.UserNotFoundException;
+import mops.gruppen2.domain.helper.ValidationHelper;
+import mops.gruppen2.domain.model.group.wrapper.Body;
+import mops.gruppen2.domain.model.group.wrapper.Description;
+import mops.gruppen2.domain.model.group.wrapper.Limit;
+import mops.gruppen2.domain.model.group.wrapper.Link;
+import mops.gruppen2.domain.model.group.wrapper.Parent;
+import mops.gruppen2.domain.model.group.wrapper.Title;
+
+import javax.validation.Valid;
+import java.time.LocalDateTime;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import java.util.stream.Collectors;
+
+/**
+ * Repräsentiert den aggregierten Zustand einer Gruppe.
+ *
+ * <p>
+ * Muss beim Start gesetzt werden: groupid, meta
+ */
+@Log4j2
+@EqualsAndHashCode(onlyExplicitlyIncluded = true)
+@ToString(onlyExplicitlyIncluded = true)
+public class Group {
+
+    // Metainformationen
+    @EqualsAndHashCode.Include
+    @ToString.Include
+    private UUID groupid;
+
+    @Getter
+    private Type type = Type.PRIVATE;
+
+    private Parent parent = Parent.EMPTY();
+
+    private Limit limit = Limit.DEFAULT(); // Add initial user
+
+    private Link link = Link.RANDOM();
+
+    @ToString.Include
+    private GroupMeta meta = GroupMeta.EMPTY();
+
+    private GroupOptions options = GroupOptions.DEFAULT();
+
+    //@ToString.Exclude
+    //private LocalDateTime age;
+
+    // Inhalt
+    private Title title;
+
+    private Description description;
+
+    private Body body;
+
+    // Integrationen
+
+    // Teilnehmer
+    private Map<String, Membership> memberships = new HashMap<>();
+
+
+    // ####################################### Members ###########################################
+
+    public List<User> getMembers() {
+        return SortHelper.sortByMemberRole(new ArrayList<>(memberships.values())).stream()
+                         .map(Membership::getUser)
+                         .collect(Collectors.toList());
+    }
+
+    public List<User> getRegulars() {
+        return memberships.values().stream()
+                          .map(Membership::getUser)
+                          .filter(member -> isRegular(member.getId()))
+                          .collect(Collectors.toList());
+    }
+
+    public List<User> getAdmins() {
+        return memberships.values().stream()
+                          .map(Membership::getUser)
+                          .filter(member -> isAdmin(member.getId()))
+                          .collect(Collectors.toList());
+    }
+
+    public Role getRole(String userid) {
+        return memberships.get(userid).getRole();
+    }
+
+    public void addMember(String target, User user) throws UserAlreadyExistsException, GroupFullException {
+        ValidationHelper.throwIfMember(this, target);
+        ValidationHelper.throwIfGroupFull(this);
+
+        memberships.put(target, new Membership(user, Role.REGULAR));
+    }
+
+    public void kickMember(String target) throws UserNotFoundException, LastAdminException {
+        ValidationHelper.throwIfNoMember(this, target);
+        ValidationHelper.throwIfLastAdmin(this, target);
+
+        memberships.remove(target);
+    }
+
+    public void memberPutRole(String target, Role role) throws UserNotFoundException, LastAdminException {
+        ValidationHelper.throwIfNoMember(this, target);
+        if (role == Role.REGULAR) {
+            ValidationHelper.throwIfLastAdmin(this, target);
+        }
+
+        memberships.put(target, memberships.get(target).setRole(role));
+    }
+
+    public boolean isMember(String target) {
+        return memberships.containsKey(target);
+    }
+
+    public boolean isAdmin(String target) throws UserNotFoundException {
+        ValidationHelper.throwIfNoMember(this, target);
+
+        return memberships.get(target).getRole() == Role.ADMIN;
+    }
+
+    public boolean isRegular(String target) throws UserNotFoundException {
+        ValidationHelper.throwIfNoMember(this, target);
+
+        return memberships.get(target).getRole() == Role.REGULAR;
+    }
+
+
+    // ######################################### Getters #########################################
+
+
+    public UUID getId() {
+        return groupid;
+    }
+
+    public UUID getParent() {
+        return parent.getGroupid();
+    }
+
+    public long getLimit() {
+        return limit.getValue();
+    }
+
+    public String getTitle() {
+        return title.toString();
+    }
+
+    public String getDescription() {
+        return description.getValue();
+    }
+
+    public String getLink() {
+        return link.getValue();
+    }
+
+    public String creator() {
+        return meta.getCreator();
+    }
+
+    public long version() {
+        return meta.getVersion();
+    }
+
+    public LocalDateTime creationDate() {
+        return meta.getCreationDate();
+    }
+
+    public int size() {
+        return memberships.size();
+    }
+
+    public boolean isFull() {
+        return size() >= limit.getValue();
+    }
+
+    public boolean isEmpty() {
+        return size() == 0;
+    }
+
+    public boolean isPublic() {
+        return type == Type.PUBLIC;
+    }
+
+    public boolean isPrivate() {
+        return type == Type.PRIVATE;
+    }
+
+    public boolean isLecture() {
+        return type == Type.LECTURE;
+    }
+
+
+    // ######################################## Setters ##########################################
+
+
+    public void setId(UUID groupid) throws BadArgumentException {
+        if (this.groupid != null) {
+            throw new BadArgumentException("GruppenId bereits gesetzt.");
+        }
+
+        this.groupid = groupid;
+    }
+
+    public void setType(String exec, Type type) throws NoAccessException {
+        ValidationHelper.throwIfNoAdmin(this, exec);
+
+        this.type = type;
+    }
+
+    public void setTitle(String exec, @Valid Title title) throws NoAccessException {
+        ValidationHelper.throwIfNoAdmin(this, exec);
+
+        this.title = title;
+    }
+
+    public void setDescription(String exec, @Valid Description description) throws NoAccessException {
+        ValidationHelper.throwIfNoAdmin(this, exec);
+
+        this.description = description;
+    }
+
+    public void setLimit(String exec, @Valid Limit limit) throws NoAccessException, BadArgumentException {
+        ValidationHelper.throwIfNoAdmin(this, exec);
+
+        if (size() > limit.getValue()) {
+            throw new BadArgumentException("Das Userlimit ist zu klein für die Gruppe.");
+        }
+
+        this.limit = limit;
+    }
+
+    public void setParent(String exec, @Valid Parent parent) throws NoAccessException {
+        ValidationHelper.throwIfNoAdmin(this, exec);
+
+        this.parent = parent;
+    }
+
+    public void setLink(String exec, @Valid Link link) throws NoAccessException {
+        ValidationHelper.throwIfNoAdmin(this, exec);
+
+        this.link = link;
+    }
+
+    public void update(long version) throws IdMismatchException {
+        meta = meta.setVersion(version);
+    }
+
+    public void setCreator(String target) throws BadArgumentException {
+        meta = meta.setCreator(target);
+    }
+
+    public void setCreationDate(LocalDateTime date) throws BadArgumentException {
+        meta = meta.setCreationDate(date);
+    }
+
+
+    // ######################################### Util ############################################
+
+
+    public void destroy(String userid) throws NoAccessException {
+        ValidationHelper.throwIfNoAdmin(this, userid);
+
+        groupid = null;
+        parent = null;
+        type = null;
+        title = null;
+        description = null;
+        limit = null;
+        memberships = null;
+        link = null;
+        meta = null;
+        options = null;
+        body = null;
+    }
+
+    public String format() {
+        return title + " " + description;
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/model/group/GroupMeta.java b/src/main/java/mops/gruppen2/domain/model/group/GroupMeta.java
new file mode 100644
index 0000000..de60300
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/model/group/GroupMeta.java
@@ -0,0 +1,47 @@
+package mops.gruppen2.domain.model.group;
+
+import lombok.ToString;
+import lombok.Value;
+import lombok.extern.log4j.Log4j2;
+import mops.gruppen2.domain.exception.BadArgumentException;
+import mops.gruppen2.domain.exception.IdMismatchException;
+
+import java.time.LocalDateTime;
+
+@Log4j2
+@Value
+@ToString
+public class GroupMeta {
+
+    long version;
+    String creator;
+    LocalDateTime creationDate;
+
+    public GroupMeta setVersion(long version) throws IdMismatchException {
+        if (this.version >= version) {
+            throw new IdMismatchException("Die Gruppe ist bereits auf einem neueren Stand.");
+        }
+
+        return new GroupMeta(version, creator, creationDate);
+    }
+
+    public GroupMeta setCreator(String userid) throws BadArgumentException {
+        if (creator != null) {
+            throw new BadArgumentException("Gruppe hat schon einen Ersteller.");
+        }
+
+        return new GroupMeta(version, userid, creationDate);
+    }
+
+    public GroupMeta setCreationDate(LocalDateTime date) throws BadArgumentException {
+        if (creationDate != null) {
+            throw new BadArgumentException("Gruppe hat schon ein Erstellungsdatum.");
+        }
+
+        return new GroupMeta(version, creator, date);
+    }
+
+    public static GroupMeta EMPTY() {
+        return new GroupMeta(0, null, null);
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/model/group/GroupOptions.java b/src/main/java/mops/gruppen2/domain/model/group/GroupOptions.java
new file mode 100644
index 0000000..88d069a
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/model/group/GroupOptions.java
@@ -0,0 +1,36 @@
+package mops.gruppen2.domain.model.group;
+
+import lombok.Value;
+
+//TODO: doooooodododo
+@Value
+class GroupOptions {
+
+    // Gruppe
+    boolean showClearname;
+    boolean hasBody;
+    boolean isLeavable;
+    boolean hasLink;
+
+    String customLogo;
+    String customBackground;
+    String customTitle;
+
+    // Integrations
+    boolean hasMaterialIntegration;
+    boolean hasTermineIntegration;
+    boolean hasPortfolioIntegration;
+
+    static GroupOptions DEFAULT() {
+        return new GroupOptions(true,
+                                false,
+                                true,
+                                false,
+                                null,
+                                null,
+                                null,
+                                true,
+                                true,
+                                true);
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/model/group/Membership.java b/src/main/java/mops/gruppen2/domain/model/group/Membership.java
new file mode 100644
index 0000000..7a730ce
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/model/group/Membership.java
@@ -0,0 +1,23 @@
+package mops.gruppen2.domain.model.group;
+
+import lombok.EqualsAndHashCode;
+import lombok.Value;
+
+@Value
+@EqualsAndHashCode(onlyExplicitlyIncluded = true)
+public class Membership {
+
+    User user;
+    Role role;
+
+    // LocalDateTime age;
+
+    @Override
+    public String toString() {
+        return user.format() + ": " + role;
+    }
+
+    public Membership setRole(Role role) {
+        return new Membership(user, role);
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/model/group/Role.java b/src/main/java/mops/gruppen2/domain/model/group/Role.java
new file mode 100644
index 0000000..0b7c4d5
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/model/group/Role.java
@@ -0,0 +1,10 @@
+package mops.gruppen2.domain.model.group;
+
+public enum Role {
+    ADMIN,
+    REGULAR;
+
+    public Role toggle() {
+        return this == ADMIN ? REGULAR : ADMIN;
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/model/group/SortHelper.java b/src/main/java/mops/gruppen2/domain/model/group/SortHelper.java
new file mode 100644
index 0000000..f1f2e36
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/model/group/SortHelper.java
@@ -0,0 +1,45 @@
+package mops.gruppen2.domain.model.group;
+
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
+
+import java.util.List;
+
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
+public final class SortHelper {
+
+    /**
+     * Sortiert die übergebene Liste an Gruppen, sodass Veranstaltungen am Anfang der Liste sind.
+     *
+     * @param groups Die Liste von Gruppen die sortiert werden soll
+     */
+    public static List<Group> sortByGroupType(List<Group> groups) {
+        groups.sort((Group g1, Group g2) -> {
+            if (g1.getType() == Type.LECTURE) {
+                return -1;
+            }
+            if (g2.getType() == Type.LECTURE) {
+                return 1;
+            }
+
+            return 0;
+        });
+
+        return groups;
+    }
+
+    public static List<Membership> sortByMemberRole(List<Membership> memberships) {
+        memberships.sort((Membership m1, Membership m2) -> {
+            if (m1.getRole() == Role.ADMIN) {
+                return -1;
+            }
+            if (m2.getRole() == Role.ADMIN) {
+                return 1;
+            }
+
+            return 0;
+        });
+
+        return memberships;
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/model/Type.java b/src/main/java/mops/gruppen2/domain/model/group/Type.java
similarity index 58%
rename from src/main/java/mops/gruppen2/domain/model/Type.java
rename to src/main/java/mops/gruppen2/domain/model/group/Type.java
index 7a0740a..eae882e 100644
--- a/src/main/java/mops/gruppen2/domain/model/Type.java
+++ b/src/main/java/mops/gruppen2/domain/model/group/Type.java
@@ -1,4 +1,4 @@
-package mops.gruppen2.domain.model;
+package mops.gruppen2.domain.model.group;
 
 public enum Type {
     PUBLIC,
diff --git a/src/main/java/mops/gruppen2/domain/model/User.java b/src/main/java/mops/gruppen2/domain/model/group/User.java
similarity index 69%
rename from src/main/java/mops/gruppen2/domain/model/User.java
rename to src/main/java/mops/gruppen2/domain/model/group/User.java
index 98f60d1..07ec8f1 100644
--- a/src/main/java/mops/gruppen2/domain/model/User.java
+++ b/src/main/java/mops/gruppen2/domain/model/group/User.java
@@ -1,26 +1,32 @@
-package mops.gruppen2.domain.model;
+package mops.gruppen2.domain.model.group;
 
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.AccessLevel;
 import lombok.AllArgsConstructor;
 import lombok.EqualsAndHashCode;
-import lombok.ToString;
+import lombok.Getter;
 import lombok.Value;
+import lombok.extern.log4j.Log4j2;
 import org.keycloak.KeycloakPrincipal;
 import org.keycloak.adapters.springsecurity.token.KeycloakAuthenticationToken;
 
+@Log4j2
 @Value
 @AllArgsConstructor
-@ToString
 public class User {
 
     @EqualsAndHashCode.Include
+    @Getter(AccessLevel.NONE)
+    @JsonProperty("id")
     String userid;
 
+    @JsonProperty("givenname")
     String givenname;
 
-    @ToString.Exclude
+    @JsonProperty("familyname")
     String familyname;
 
-    @ToString.Exclude
+    @JsonProperty("mail")
     String email;
 
     public User(KeycloakAuthenticationToken token) {
@@ -42,4 +48,12 @@ public class User {
         familyname = "";
         email = "";
     }
+
+    public String getId() {
+        return userid;
+    }
+
+    public String format() {
+        return givenname + " " + familyname;
+    }
 }
diff --git a/src/main/java/mops/gruppen2/domain/model/group/wrapper/Body.java b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Body.java
new file mode 100644
index 0000000..791b527
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Body.java
@@ -0,0 +1,8 @@
+package mops.gruppen2.domain.model.group.wrapper;
+
+import lombok.Value;
+
+//TODO: do it
+@Value
+public class Body {
+}
diff --git a/src/main/java/mops/gruppen2/domain/model/Description.java b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Description.java
similarity index 56%
rename from src/main/java/mops/gruppen2/domain/model/Description.java
rename to src/main/java/mops/gruppen2/domain/model/group/wrapper/Description.java
index 7db3a30..c37c29a 100644
--- a/src/main/java/mops/gruppen2/domain/model/Description.java
+++ b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Description.java
@@ -1,21 +1,21 @@
-package mops.gruppen2.domain.model;
+package mops.gruppen2.domain.model.group.wrapper;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
 import lombok.Value;
 
-import javax.validation.constraints.NotBlank;
+import javax.validation.constraints.NotNull;
 import javax.validation.constraints.Size;
 
 @Value
 public class Description {
 
-    @NotBlank
+    @NotNull
     @Size(min = 4, max = 512)
-    @JsonProperty("desc")
-    String groupDescription;
+    @JsonProperty("value")
+    String value;
 
     @Override
     public String toString() {
-        return groupDescription;
+        return value;
     }
 }
diff --git a/src/main/java/mops/gruppen2/domain/model/Limit.java b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Limit.java
similarity index 51%
rename from src/main/java/mops/gruppen2/domain/model/Limit.java
rename to src/main/java/mops/gruppen2/domain/model/group/wrapper/Limit.java
index 60c0e08..b06d69e 100644
--- a/src/main/java/mops/gruppen2/domain/model/Limit.java
+++ b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Limit.java
@@ -1,21 +1,27 @@
-package mops.gruppen2.domain.model;
+package mops.gruppen2.domain.model.group.wrapper;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
 import lombok.Value;
 
 import javax.validation.constraints.Max;
 import javax.validation.constraints.Min;
+import javax.validation.constraints.NotNull;
 
 @Value
 public class Limit {
 
+    @NotNull
     @Min(1)
     @Max(999_999)
-    @JsonProperty("limit")
-    long userLimit;
+    @JsonProperty("value")
+    long value;
+
+    public static Limit DEFAULT() {
+        return new Limit(1);
+    }
 
     @Override
     public String toString() {
-        return String.valueOf(userLimit);
+        return String.valueOf(value);
     }
 }
diff --git a/src/main/java/mops/gruppen2/domain/model/group/wrapper/Link.java b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Link.java
new file mode 100644
index 0000000..a79db9a
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Link.java
@@ -0,0 +1,21 @@
+package mops.gruppen2.domain.model.group.wrapper;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.Value;
+
+import javax.validation.constraints.NotNull;
+import javax.validation.constraints.Size;
+import java.util.UUID;
+
+@Value
+public class Link {
+
+    @NotNull
+    @Size(min = 36, max = 36)
+    @JsonProperty("value")
+    String value;
+
+    public static Link RANDOM() {
+        return new Link(UUID.randomUUID().toString());
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/model/group/wrapper/Parent.java b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Parent.java
new file mode 100644
index 0000000..aaa93d0
--- /dev/null
+++ b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Parent.java
@@ -0,0 +1,34 @@
+package mops.gruppen2.domain.model.group.wrapper;
+
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import lombok.Value;
+import mops.gruppen2.domain.helper.CommonHelper;
+
+import javax.validation.constraints.NotBlank;
+import javax.validation.constraints.NotNull;
+import javax.validation.constraints.Size;
+import java.beans.ConstructorProperties;
+import java.util.UUID;
+
+@Value
+public class Parent {
+
+    @NotNull
+    @JsonProperty("id")
+    UUID groupid;
+
+    @ConstructorProperties("id")
+    public Parent(@NotBlank @Size(min = 36, max = 36) String parentid) {
+        groupid = UUID.fromString(parentid);
+    }
+
+    public static Parent EMPTY() {
+        return new Parent("00000000-0000-0000-0000-000000000000");
+    }
+
+    @JsonIgnore
+    public boolean isEmpty() {
+        return CommonHelper.uuidIsEmpty(groupid);
+    }
+}
diff --git a/src/main/java/mops/gruppen2/domain/model/Title.java b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Title.java
similarity index 57%
rename from src/main/java/mops/gruppen2/domain/model/Title.java
rename to src/main/java/mops/gruppen2/domain/model/group/wrapper/Title.java
index 6c410df..2bcc8ee 100644
--- a/src/main/java/mops/gruppen2/domain/model/Title.java
+++ b/src/main/java/mops/gruppen2/domain/model/group/wrapper/Title.java
@@ -1,21 +1,21 @@
-package mops.gruppen2.domain.model;
+package mops.gruppen2.domain.model.group.wrapper;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
 import lombok.Value;
 
-import javax.validation.constraints.NotBlank;
+import javax.validation.constraints.NotNull;
 import javax.validation.constraints.Size;
 
 @Value
 public class Title {
 
-    @NotBlank
+    @NotNull
     @Size(min = 4, max = 128)
-    @JsonProperty("title")
-    String groupTitle;
+    @JsonProperty("value")
+    String value;
 
     @Override
     public String toString() {
-        return groupTitle;
+        return value;
     }
 }
diff --git a/src/main/java/mops/gruppen2/domain/service/EventStoreService.java b/src/main/java/mops/gruppen2/domain/service/EventStoreService.java
index a2b8eaa..4ee3328 100644
--- a/src/main/java/mops/gruppen2/domain/service/EventStoreService.java
+++ b/src/main/java/mops/gruppen2/domain/service/EventStoreService.java
@@ -1,35 +1,40 @@
 package mops.gruppen2.domain.service;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
+import lombok.RequiredArgsConstructor;
 import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.event.AddUserEvent;
+import mops.gruppen2.aspect.annotation.TraceMethodCalls;
+import mops.gruppen2.domain.event.AddMemberEvent;
 import mops.gruppen2.domain.event.CreateGroupEvent;
 import mops.gruppen2.domain.event.Event;
+import mops.gruppen2.domain.event.EventType;
 import mops.gruppen2.domain.exception.BadPayloadException;
-import mops.gruppen2.domain.helper.IdHelper;
+import mops.gruppen2.domain.exception.InvalidInviteException;
 import mops.gruppen2.domain.helper.JsonHelper;
-import mops.gruppen2.domain.model.User;
 import mops.gruppen2.persistance.EventRepository;
 import mops.gruppen2.persistance.dto.EventDTO;
 import org.springframework.stereotype.Service;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.UUID;
 import java.util.stream.Collectors;
 
-@Service
+import static mops.gruppen2.domain.event.EventType.CREATEGROUP;
+import static mops.gruppen2.domain.event.EventType.DESTROYGROUP;
+import static mops.gruppen2.domain.event.EventType.SETLINK;
+import static mops.gruppen2.domain.helper.CommonHelper.eventTypesToString;
+import static mops.gruppen2.domain.helper.CommonHelper.uuidsToString;
+
 @Log4j2
+@RequiredArgsConstructor
+@Service
+@TraceMethodCalls
 public class EventStoreService {
 
     private final EventRepository eventStore;
 
-    public EventStoreService(EventRepository eventStore) {
-        this.eventStore = eventStore;
-    }
-
 
     //########################################### SAVE ###########################################
 
@@ -67,7 +72,7 @@ public class EventStoreService {
     //########################################### DTOs ###########################################
 
 
-    static List<EventDTO> getDTOsFromEvents(List<Event> events) {
+    private static List<EventDTO> getDTOsFromEvents(List<Event> events) {
         return events.stream()
                      .map(EventStoreService::getDTOFromEvent)
                      .collect(Collectors.toList());
@@ -80,13 +85,15 @@ public class EventStoreService {
      *
      * @return EventDTO (Neues DTO)
      */
-    static EventDTO getDTOFromEvent(Event event) {
+    private static EventDTO getDTOFromEvent(Event event) {
         try {
             String payload = JsonHelper.serializeEvent(event);
             return new EventDTO(null,
                                 event.getGroupid().toString(),
-                                event.getUserid(),
-                                getEventType(event),
+                                event.getVersion(),
+                                event.getExec(),
+                                event.getTarget(),
+                                event.getType(),
                                 payload);
         } catch (JsonProcessingException e) {
             log.error("Event ({}) konnte nicht serialisiert werden!", event, e);
@@ -116,19 +123,6 @@ public class EventStoreService {
         }
     }
 
-    /**
-     * Gibt den Eventtyp als String wieder.
-     *
-     * @param event Event dessen Typ abgefragt werden soll
-     *
-     * @return Der Name des Typs des Events
-     */
-    private static String getEventType(Event event) {
-        int lastDot = event.getClass().getName().lastIndexOf('.');
-
-        return event.getClass().getName().substring(lastDot + 1);
-    }
-
 
     // ######################################## QUERIES ##########################################
 
@@ -176,8 +170,8 @@ public class EventStoreService {
      * @return GruppenIds (UUID) als Liste
      */
     List<UUID> findExistingGroupIds() {
-        List<Event> createEvents = findLatestEventsFromGroupsByType("CreateGroupEvent",
-                                                                    "DeleteGroupEvent");
+        List<Event> createEvents = findLatestEventsFromGroupsByType(CREATEGROUP,
+                                                                    DESTROYGROUP);
 
         return createEvents.stream()
                            .filter(event -> event instanceof CreateGroupEvent)
@@ -188,11 +182,18 @@ public class EventStoreService {
     /**
      * Liefert Gruppen-Ids von existierenden (ungelöschten) Gruppen, in welchen der User teilnimmt.
      *
+     * <p>
+     * Vorgang:
+     * Finde für jede Gruppe das letzte Add- oder Kick-Event, welches den User betrifft
+     * Finde für jede Gruppe das letzte Destroy-Event
+     * Entferne alle alle Events von Gruppen, welche ein Destroy-Event haben
+     * Gebe die Gruppen zurück, auf welche sich die Add-Events beziehen
+     *
      * @return GruppenIds (UUID) als Liste
      */
-    public List<UUID> findExistingUserGroups(User user) {
-        List<Event> userEvents = findLatestEventsFromGroupsByUser(user);
-        List<UUID> deletedIds = findLatestEventsFromGroupsByType("DeleteGroupEvent")
+    public List<UUID> findExistingUserGroups(String userid) {
+        List<Event> userEvents = findLatestEventsFromGroupsByUser(userid);
+        List<UUID> deletedIds = findLatestEventsFromGroupsByType(DESTROYGROUP)
                 .stream()
                 .map(Event::getGroupid)
                 .collect(Collectors.toList());
@@ -200,11 +201,25 @@ public class EventStoreService {
         userEvents.removeIf(event -> deletedIds.contains(event.getGroupid()));
 
         return userEvents.stream()
-                         .filter(event -> event instanceof AddUserEvent)
+                         .filter(event -> event instanceof AddMemberEvent)
                          .map(Event::getGroupid)
                          .collect(Collectors.toList());
     }
 
+    public UUID findGroupByLink(String link) {
+        List<Event> groupEvents = findEventsByType(eventTypesToString(SETLINK));
+
+        if (groupEvents.size() > 1) {
+            throw new InvalidInviteException("Es existieren mehrere Gruppen mit demselben Link.");
+        }
+
+        if (groupEvents.isEmpty()) {
+            throw new InvalidInviteException("Link nicht gefunden.");
+        }
+
+        return groupEvents.get(0).getGroupid();
+    }
+
 
     // #################################### SIMPLE QUERIES #######################################
 
@@ -219,32 +234,32 @@ public class EventStoreService {
             return eventStore.findMaxEventId();
         } catch (NullPointerException e) {
             log.debug("Keine Events vorhanden!");
-            return 0;
+            return 1;
         }
     }
 
     List<Event> findEventsByType(String... types) {
-        return getEventsFromDTOs(eventStore.findEventDTOsByType(Arrays.asList(types)));
+        return getEventsFromDTOs(eventStore.findEventDTOsByType(types));
     }
 
     List<Event> findEventsByType(String type) {
-        return getEventsFromDTOs(eventStore.findEventDTOsByType(Collections.singletonList(type)));
+        return getEventsFromDTOs(eventStore.findEventDTOsByType(type));
     }
 
     List<Event> findEventsByGroupAndType(List<UUID> groupIds, String... types) {
-        return getEventsFromDTOs(eventStore.findEventDTOsByGroupAndType(Arrays.asList(types),
-                                                                        IdHelper.uuidsToString(groupIds)));
+        return getEventsFromDTOs(eventStore.findEventDTOsByGroupAndType(uuidsToString(groupIds),
+                                                                        types));
     }
 
     /**
      * Sucht zu jeder Gruppe das letzte Add- oder DeleteUserEvent heraus, welches den übergebenen User betrifft.
      *
-     * @param user User, zu welchem die Events gesucht werden
+     * @param userid User, zu welchem die Events gesucht werden
      *
      * @return Eine Liste von einem Add- oder DeleteUserEvent pro Gruppe
      */
-    private List<Event> findLatestEventsFromGroupsByUser(User user) {
-        return getEventsFromDTOs(eventStore.findLatestEventDTOsPartitionedByGroupByUser(user.getUserid()));
+    private List<Event> findLatestEventsFromGroupsByUser(String userid) {
+        return getEventsFromDTOs(eventStore.findLatestEventDTOsPartitionedByGroupByUser(userid));
     }
 
 
@@ -255,7 +270,7 @@ public class EventStoreService {
      *
      * @return Eine Liste von einem Event pro Gruppe
      */
-    private List<Event> findLatestEventsFromGroupsByType(String... types) {
-        return getEventsFromDTOs(eventStore.findLatestEventDTOsPartitionedByGroupByType(Arrays.asList(types)));
+    private List<Event> findLatestEventsFromGroupsByType(EventType... types) {
+        return getEventsFromDTOs(eventStore.findLatestEventDTOsPartitionedByGroupByType(eventTypesToString(types)));
     }
 }
diff --git a/src/main/java/mops/gruppen2/domain/service/GroupService.java b/src/main/java/mops/gruppen2/domain/service/GroupService.java
index 4fd0494..237db1d 100644
--- a/src/main/java/mops/gruppen2/domain/service/GroupService.java
+++ b/src/main/java/mops/gruppen2/domain/service/GroupService.java
@@ -1,26 +1,33 @@
 package mops.gruppen2.domain.service;
 
+import lombok.RequiredArgsConstructor;
 import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.event.AddUserEvent;
+import mops.gruppen2.domain.event.AddMemberEvent;
 import mops.gruppen2.domain.event.CreateGroupEvent;
-import mops.gruppen2.domain.event.DeleteGroupEvent;
-import mops.gruppen2.domain.event.DeleteUserEvent;
+import mops.gruppen2.domain.event.DestroyGroupEvent;
 import mops.gruppen2.domain.event.Event;
-import mops.gruppen2.domain.event.UpdateGroupDescriptionEvent;
-import mops.gruppen2.domain.event.UpdateGroupTitleEvent;
+import mops.gruppen2.domain.event.KickMemberEvent;
+import mops.gruppen2.domain.event.SetDescriptionEvent;
+import mops.gruppen2.domain.event.SetInviteLinkEvent;
+import mops.gruppen2.domain.event.SetLimitEvent;
+import mops.gruppen2.domain.event.SetParentEvent;
+import mops.gruppen2.domain.event.SetTitleEvent;
+import mops.gruppen2.domain.event.SetTypeEvent;
 import mops.gruppen2.domain.event.UpdateRoleEvent;
-import mops.gruppen2.domain.event.UpdateUserLimitEvent;
 import mops.gruppen2.domain.exception.EventException;
 import mops.gruppen2.domain.helper.ValidationHelper;
-import mops.gruppen2.domain.model.Description;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Limit;
-import mops.gruppen2.domain.model.Role;
-import mops.gruppen2.domain.model.Title;
-import mops.gruppen2.domain.model.Type;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Role;
+import mops.gruppen2.domain.model.group.Type;
+import mops.gruppen2.domain.model.group.User;
+import mops.gruppen2.domain.model.group.wrapper.Description;
+import mops.gruppen2.domain.model.group.wrapper.Limit;
+import mops.gruppen2.domain.model.group.wrapper.Link;
+import mops.gruppen2.domain.model.group.wrapper.Parent;
+import mops.gruppen2.domain.model.group.wrapper.Title;
 import org.springframework.stereotype.Service;
 
+import java.time.LocalDateTime;
 import java.util.List;
 import java.util.UUID;
 
@@ -28,51 +35,47 @@ import java.util.UUID;
  * Behandelt Aufgaben, welche sich auf eine Gruppe beziehen.
  * Es werden übergebene Gruppen bearbeitet und dementsprechend Events erzeugt und gespeichert.
  */
-@Service
 @Log4j2
+@RequiredArgsConstructor
+@Service
 public class GroupService {
 
     private final EventStoreService eventStoreService;
-    private final InviteService inviteService;
-
-    public GroupService(EventStoreService eventStoreService, InviteService inviteService) {
-        this.eventStoreService = eventStoreService;
-        this.inviteService = inviteService;
-    }
-
 
     // ################################# GRUPPE ERSTELLEN ########################################
 
 
-    /**
-     * Erzeugt eine neue Gruppe und erzeugt nötige Events für die Initiale Setzung der Attribute.
-     *
-     * @param user        Keycloak-Account
-     * @param title       Gruppentitel
-     * @param description Gruppenbeschreibung
-     */
-    public Group createGroup(User user,
-                             Title title,
-                             Description description,
-                             Type type,
-                             Limit userLimit,
-                             UUID parent) {
+    public Group createGroup(String exec) {
+        return createGroup(UUID.randomUUID(), exec, LocalDateTime.now());
+    }
 
-        // Regeln:
-        // isPrivate -> !isLecture
-        // isLecture -> !isPrivate
-        Group group = createGroup(user, parent, type);
+    public void initGroupMembers(Group group,
+                                 String exec,
+                                 String target,
+                                 User user,
+                                 Limit limit) {
 
-        // Die Reihenfolge ist wichtig, da der ausführende User Admin sein muss
-        addUser(user, group);
-        updateRole(user, group, Role.ADMIN);
-        updateTitle(user, group, title);
-        updateDescription(user, group, description);
-        updateUserLimit(user, group, userLimit);
+        addMember(group, exec, target, user);
+        updateRole(group, exec, target, Role.ADMIN);
+        setLimit(group, exec, limit);
+    }
 
-        inviteService.createLink(group);
+    public void initGroupMeta(Group group,
+                              String exec,
+                              Type type,
+                              Parent parent) {
 
-        return group;
+        setType(group, exec, type);
+        setParent(group, exec, parent);
+    }
+
+    public void initGroupText(Group group,
+                              String exec,
+                              Title title,
+                              Description description) {
+
+        setTitle(group, exec, title);
+        setDescription(group, exec, description);
     }
 
 
@@ -87,12 +90,12 @@ public class GroupService {
      *
      * @param newUsers Userliste
      * @param group    Gruppe
-     * @param user     Ausführender User
+     * @param exec     Ausführender User
      */
-    public void addUsersToGroup(List<User> newUsers, Group group, User user) {
-        updateUserLimit(user, group, getAdjustedUserLimit(newUsers, group));
+    public void addUsersToGroup(Group group, String exec, List<User> newUsers) {
+        setLimit(group, exec, getAdjustedUserLimit(newUsers, group));
 
-        newUsers.forEach(newUser -> addUserSilent(newUser, group));
+        newUsers.forEach(newUser -> addUserSilent(group, exec, newUser.getId(), newUser));
     }
 
     /**
@@ -106,24 +109,20 @@ public class GroupService {
      * @return Das neue Teilnehmermaximum
      */
     private static Limit getAdjustedUserLimit(List<User> newUsers, Group group) {
-        return new Limit(Math.max((long) group.getMembers().size() + newUsers.size(), group.getLimit().getUserLimit()));
+        return new Limit(Math.max((long) group.size() + newUsers.size(), group.getLimit()));
     }
 
     /**
      * Wechselt die Rolle eines Teilnehmers von Admin zu Member oder andersherum.
      * Überprüft, ob der User Mitglied ist und ob er der letzte Admin ist.
      *
-     * @param user  Teilnehmer, welcher geändert wird
-     * @param group Gruppe, in welcher sih der Teilnehmer befindet
+     * @param target Teilnehmer, welcher geändert wird
+     * @param group  Gruppe, in welcher sih der Teilnehmer befindet
      *
      * @throws EventException Falls der User nicht gefunden wird
      */
-    public void toggleMemberRole(User user, Group group) throws EventException {
-        ValidationHelper.throwIfNoMember(group, user);
-        ValidationHelper.throwIfLastAdmin(user, group);
-
-        Role role = group.getRoles().get(user.getUserid());
-        updateRole(user, group, role.toggle());
+    public void toggleMemberRole(Group group, String exec, String target) {
+        updateRole(group, exec, target, group.getRole(target).toggle());
     }
 
 
@@ -134,59 +133,44 @@ public class GroupService {
     /**
      * Erzeugt eine Gruppe, speichert diese und gibt diese zurück.
      */
-    private Group createGroup(User user, UUID parent, Type type) {
-        Event event = new CreateGroupEvent(UUID.randomUUID(),
-                                           user,
-                                           parent,
-                                           type);
+    private Group createGroup(UUID groupid, String exec, LocalDateTime date) {
+        Event event = new CreateGroupEvent(groupid,
+                                           exec,
+                                           date);
         Group group = new Group();
-        event.apply(group);
-
-        eventStoreService.saveEvent(event);
+        applyAndSave(group, event);
 
         return group;
     }
 
-    /**
-     * Erzeugt, speichert ein AddUserEvent und wendet es auf eine Gruppe an.
-     * Prüft, ob der Nutzer schon Mitglied ist und ob Gruppe voll ist.
-     */
-    public void addUser(User user, Group group) {
-        ValidationHelper.throwIfMember(group, user);
-        ValidationHelper.throwIfGroupFull(group);
-
-        Event event = new AddUserEvent(group, user);
-        event.apply(group);
-
-        eventStoreService.saveEvent(event);
-    }
-
     /**
      * Dasselbe wie addUser(), aber exceptions werden abgefangen und nicht geworfen.
      */
-    private void addUserSilent(User user, Group group) {
+    private void addUserSilent(Group group, String exec, String target, User user) {
         try {
-            addUser(user, group);
+            addMember(group, exec, target, user);
         } catch (Exception e) {
             log.debug("Doppelter User {} wurde nicht zu Gruppe {} hinzugefügt!", user, group);
         }
     }
 
+    /**
+     * Erzeugt, speichert ein AddUserEvent und wendet es auf eine Gruppe an.
+     * Prüft, ob der Nutzer schon Mitglied ist und ob Gruppe voll ist.
+     */
+    public void addMember(Group group, String exec, String target, User user) {
+        applyAndSave(group, new AddMemberEvent(group, exec, target, user));
+    }
+
     /**
      * Erzeugt, speichert ein DeleteUserEvent und wendet es auf eine Gruppe an.
      * Prüft, ob der Nutzer Mitglied ist und ob er der letzte Admin ist.
      */
-    public void deleteUser(User user, Group group) throws EventException {
-        ValidationHelper.throwIfNoMember(group, user);
-        ValidationHelper.throwIfLastAdmin(user, group);
+    public void deleteUser(Group group, String exec, String target) {
+        applyAndSave(group, new KickMemberEvent(group, exec, target));
 
         if (ValidationHelper.checkIfGroupEmpty(group)) {
-            deleteGroup(user, group);
-        } else {
-            Event event = new DeleteUserEvent(group, user);
-            event.apply(group);
-
-            eventStoreService.saveEvent(event);
+            deleteGroup(group, target);
         }
     }
 
@@ -194,14 +178,8 @@ public class GroupService {
      * Erzeugt, speichert ein DeleteGroupEvent und wendet es auf eine Gruppe an.
      * Prüft, ob der Nutzer Admin ist.
      */
-    public void deleteGroup(User user, Group group) {
-        ValidationHelper.throwIfNoAdmin(group, user);
-
-        Event event = new DeleteGroupEvent(group, user);
-        event.apply(group);
-        inviteService.destroyLink(group);
-
-        eventStoreService.saveEvent(event);
+    public void deleteGroup(Group group, String exec) {
+        applyAndSave(group, new DestroyGroupEvent(group, exec));
     }
 
     /**
@@ -209,17 +187,8 @@ public class GroupService {
      * Prüft, ob der Nutzer Admin ist und ob der Titel valide ist.
      * Bei keiner Änderung wird nichts erzeugt.
      */
-    public void updateTitle(User user, Group group, Title title) {
-        ValidationHelper.throwIfNoAdmin(group, user);
-
-        if (title.equals(group.getTitle())) {
-            return;
-        }
-
-        Event event = new UpdateGroupTitleEvent(group, user, title);
-        event.apply(group);
-
-        eventStoreService.saveEvent(event);
+    public void setTitle(Group group, String exec, Title title) {
+        applyAndSave(group, new SetTitleEvent(group, exec, title));
     }
 
     /**
@@ -227,17 +196,8 @@ public class GroupService {
      * Prüft, ob der Nutzer Admin ist und ob die Beschreibung valide ist.
      * Bei keiner Änderung wird nichts erzeugt.
      */
-    public void updateDescription(User user, Group group, Description description) {
-        ValidationHelper.throwIfNoAdmin(group, user);
-
-        if (description.equals(group.getDescription())) {
-            return;
-        }
-
-        Event event = new UpdateGroupDescriptionEvent(group, user, description);
-        event.apply(group);
-
-        eventStoreService.saveEvent(event);
+    public void setDescription(Group group, String exec, Description description) {
+        applyAndSave(group, new SetDescriptionEvent(group, exec, description));
     }
 
     /**
@@ -245,17 +205,8 @@ public class GroupService {
      * Prüft, ob der Nutzer Mitglied ist.
      * Bei keiner Änderung wird nichts erzeugt.
      */
-    private void updateRole(User user, Group group, Role role) {
-        ValidationHelper.throwIfNoMember(group, user);
-
-        if (role == group.getRoles().get(user.getUserid())) {
-            return;
-        }
-
-        Event event = new UpdateRoleEvent(group, user, role);
-        event.apply(group);
-
-        eventStoreService.saveEvent(event);
+    private void updateRole(Group group, String exec, String target, Role role) {
+        applyAndSave(group, new UpdateRoleEvent(group, exec, target, role));
     }
 
     /**
@@ -263,20 +214,24 @@ public class GroupService {
      * Prüft, ob der Nutzer Admin ist und ob das Limit valide ist.
      * Bei keiner Änderung wird nichts erzeugt.
      */
-    public void updateUserLimit(User user, Group group, Limit userLimit) {
-        ValidationHelper.throwIfNoAdmin(group, user);
+    public void setLimit(Group group, String exec, Limit userLimit) {
+        applyAndSave(group, new SetLimitEvent(group, exec, userLimit));
+    }
 
-        if (userLimit == group.getLimit()) {
-            return;
-        }
+    public void setParent(Group group, String exec, Parent parent) {
+        applyAndSave(group, new SetParentEvent(group, exec, parent));
+    }
 
-        Event event;
-        if (userLimit.getUserLimit() < group.getMembers().size()) {
-            event = new UpdateUserLimitEvent(group, user, new Limit(group.getMembers().size()));
-        } else {
-            event = new UpdateUserLimitEvent(group, user, userLimit);
-        }
+    public void setLink(Group group, String exec, Link link) {
+        applyAndSave(group, new SetInviteLinkEvent(group, exec, link));
+    }
 
+    private void setType(Group group, String exec, Type type) {
+        applyAndSave(group, new SetTypeEvent(group, exec, type));
+    }
+
+    private void applyAndSave(Group group, Event event) throws EventException {
+        event.init(group.version() + 1);
         event.apply(group);
 
         eventStoreService.saveEvent(event);
diff --git a/src/main/java/mops/gruppen2/domain/service/InviteService.java b/src/main/java/mops/gruppen2/domain/service/InviteService.java
deleted file mode 100644
index 669b3dd..0000000
--- a/src/main/java/mops/gruppen2/domain/service/InviteService.java
+++ /dev/null
@@ -1,54 +0,0 @@
-package mops.gruppen2.domain.service;
-
-import lombok.extern.log4j.Log4j2;
-import mops.gruppen2.domain.exception.InvalidInviteException;
-import mops.gruppen2.domain.exception.NoInviteExistException;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.persistance.InviteRepository;
-import mops.gruppen2.persistance.dto.InviteLinkDTO;
-import org.springframework.stereotype.Service;
-
-import java.util.UUID;
-
-@Service
-@Log4j2
-public class InviteService {
-
-    private final InviteRepository inviteRepository;
-
-    public InviteService(InviteRepository inviteRepository) {
-        this.inviteRepository = inviteRepository;
-    }
-
-    void createLink(Group group) {
-        inviteRepository.save(new InviteLinkDTO(null,
-                                                group.getGroupid().toString(),
-                                                UUID.randomUUID().toString()));
-
-        log.debug("Link wurde erzeugt! (Gruppe: {})", group.getGroupid());
-    }
-
-    void destroyLink(Group group) {
-        inviteRepository.deleteLinkOfGroup(group.getGroupid().toString());
-
-        log.debug("Link wurde zerstört! (Gruppe: {})", group.getGroupid());
-    }
-
-    public UUID getGroupIdFromLink(String link) {
-        try {
-            return UUID.fromString(inviteRepository.findGroupIdByLink(link));
-        } catch (Exception e) {
-            log.error("Gruppe zu Link ({}) konnte nicht gefunden werden!", link, e);
-            throw new InvalidInviteException(link);
-        }
-    }
-
-    public String getLinkByGroup(Group group) {
-        try {
-            return inviteRepository.findLinkByGroupId(group.getGroupid().toString());
-        } catch (Exception e) {
-            log.error("Link zu Gruppe ({}) konnte nicht gefunden werden!", group.getGroupid(), e);
-            throw new NoInviteExistException(group.getGroupid().toString());
-        }
-    }
-}
diff --git a/src/main/java/mops/gruppen2/domain/service/ProjectionService.java b/src/main/java/mops/gruppen2/domain/service/ProjectionService.java
index b241872..e7b64a3 100644
--- a/src/main/java/mops/gruppen2/domain/service/ProjectionService.java
+++ b/src/main/java/mops/gruppen2/domain/service/ProjectionService.java
@@ -1,37 +1,41 @@
 package mops.gruppen2.domain.service;
 
+import lombok.RequiredArgsConstructor;
 import lombok.extern.log4j.Log4j2;
 import mops.gruppen2.domain.event.Event;
 import mops.gruppen2.domain.exception.EventException;
 import mops.gruppen2.domain.exception.GroupNotFoundException;
-import mops.gruppen2.domain.helper.IdHelper;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Type;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.helper.CommonHelper;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Type;
 import org.springframework.cache.annotation.Cacheable;
 import org.springframework.stereotype.Service;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.UUID;
 import java.util.stream.Collectors;
 
+import static mops.gruppen2.domain.event.EventType.CREATEGROUP;
+import static mops.gruppen2.domain.event.EventType.SETDESCRIPTION;
+import static mops.gruppen2.domain.event.EventType.SETLIMIT;
+import static mops.gruppen2.domain.event.EventType.SETTITLE;
+import static mops.gruppen2.domain.helper.CommonHelper.eventTypesToString;
+
 /**
  * Liefert verschiedene Projektionen auf Gruppen.
  * Benötigt ausschließlich den EventStoreService.
  */
-@Service
 @Log4j2
+@RequiredArgsConstructor
+@Service
 public class ProjectionService {
 
     private final EventStoreService eventStoreService;
 
-    public ProjectionService(EventStoreService eventStoreService) {
-        this.eventStoreService = eventStoreService;
-    }
-
 
     // ################################## STATISCHE PROJEKTIONEN #################################
 
@@ -121,11 +125,16 @@ public class ProjectionService {
     @Cacheable("groups")
     public List<Group> projectPublicGroups() throws EventException {
         List<UUID> groupIds = eventStoreService.findExistingGroupIds();
+
+        if (groupIds.isEmpty()) {
+            return Collections.emptyList();
+        }
+
         List<Event> events = eventStoreService.findEventsByGroupAndType(groupIds,
-                                                                        "CreateGroupEvent",
-                                                                        "UpdateGroupDescriptionEvent",
-                                                                        "UpdateGroupTitleEvent",
-                                                                        "UpdateUserMaxEvent");
+                                                                        eventTypesToString(CREATEGROUP,
+                                                                                           SETDESCRIPTION,
+                                                                                           SETTITLE,
+                                                                                           SETLIMIT));
 
         List<Group> groups = projectGroups(events);
 
@@ -143,9 +152,14 @@ public class ProjectionService {
     @Cacheable("groups")
     public List<Group> projectLectures() {
         List<UUID> groupIds = eventStoreService.findExistingGroupIds();
+
+        if (groupIds.isEmpty()) {
+            return Collections.emptyList();
+        }
+
         List<Event> events = eventStoreService.findEventsByGroupAndType(groupIds,
-                                                                        "CreateGroupEvent",
-                                                                        "UpdateGroupTitleEvent");
+                                                                        eventTypesToString(CREATEGROUP,
+                                                                                           SETTITLE));
 
         List<Group> lectures = projectGroups(events);
 
@@ -158,17 +172,22 @@ public class ProjectionService {
      * Projiziert Gruppen, in welchen der User aktuell teilnimmt.
      * Die Gruppen enthalten nur Metainformationen: Titel und Beschreibung.
      *
-     * @param user Die Id
+     * @param userid Die Id
      *
      * @return Liste aus Gruppen
      */
     @Cacheable("groups")
-    public List<Group> projectUserGroups(User user) {
-        List<UUID> groupIds = eventStoreService.findExistingUserGroups(user);
+    public List<Group> projectUserGroups(String userid) {
+        List<UUID> groupIds = eventStoreService.findExistingUserGroups(userid);
+
+        if (groupIds.isEmpty()) {
+            return Collections.emptyList();
+        }
+
         List<Event> groupEvents = eventStoreService.findEventsByGroupAndType(groupIds,
-                                                                             "CreateGroupEvent",
-                                                                             "UpdateGroupTitleEvent",
-                                                                             "UpdateGroupDescriptionEvent");
+                                                                             eventTypesToString(CREATEGROUP,
+                                                                                                SETTITLE,
+                                                                                                SETDESCRIPTION));
 
         return projectGroups(groupEvents);
     }
@@ -185,10 +204,6 @@ public class ProjectionService {
      * @throws GroupNotFoundException Wenn die Gruppe nicht gefunden wird
      */
     public Group projectSingleGroup(UUID groupId) throws GroupNotFoundException {
-        if (IdHelper.isEmpty(groupId)) {
-            throw new GroupNotFoundException(groupId + ": " + ProjectionService.class);
-        }
-
         try {
             List<Event> events = eventStoreService.findGroupEvents(groupId);
             return projectSingleGroup(events);
@@ -198,27 +213,28 @@ public class ProjectionService {
         }
     }
 
-    /**
-     * Projiziert eine einzelne Gruppe, welche leer sein darf.
-     */
-    public Group projectParent(UUID parentId) {
-        if (IdHelper.isEmpty(parentId)) {
+    public Group projectParent(UUID parent) {
+        if (CommonHelper.uuidIsEmpty(parent)) {
             return new Group();
         }
 
-        return projectSingleGroup(parentId);
+        return projectSingleGroup(parent);
     }
 
     /**
      * Entfernt alle Gruppen, in welchen ein User teilnimmt, aus einer Gruppenliste.
      *
      * @param groups Gruppenliste, aus der entfernt wird
-     * @param user   User, welcher teilnimmt
+     * @param userid User, welcher teilnimmt
      */
-    void removeUserGroups(List<Group> groups, User user) {
-        List<UUID> userGroups = eventStoreService.findExistingUserGroups(user);
+    void removeUserGroups(List<Group> groups, String userid) {
+        List<UUID> userGroups = eventStoreService.findExistingUserGroups(userid);
 
-        groups.removeIf(group -> userGroups.contains(group.getGroupid()));
+        groups.removeIf(group -> userGroups.contains(group.getId()));
+    }
+
+    public Group projectGroupByLink(String link) {
+        return projectSingleGroup(eventStoreService.findGroupByLink(link));
     }
 }
 
diff --git a/src/main/java/mops/gruppen2/domain/service/SearchService.java b/src/main/java/mops/gruppen2/domain/service/SearchService.java
index 5e51c6b..627c964 100644
--- a/src/main/java/mops/gruppen2/domain/service/SearchService.java
+++ b/src/main/java/mops/gruppen2/domain/service/SearchService.java
@@ -2,9 +2,8 @@ package mops.gruppen2.domain.service;
 
 import lombok.extern.log4j.Log4j2;
 import mops.gruppen2.domain.exception.EventException;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Type;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.SortHelper;
 import org.springframework.cache.annotation.Cacheable;
 import org.springframework.stereotype.Service;
 
@@ -33,10 +32,10 @@ public class SearchService {
      * @throws EventException Projektionsfehler
      */
     @Cacheable("groups")
-    public List<Group> searchPublicGroups(String search, User user) throws EventException {
+    public List<Group> searchPublicGroups(String search, String userid) {
         List<Group> groups = projectionService.projectPublicGroups();
-        projectionService.removeUserGroups(groups, user);
-        sortByGroupType(groups);
+        projectionService.removeUserGroups(groups, userid);
+        SortHelper.sortByGroupType(groups);
 
         if (search.isEmpty()) {
             return groups;
@@ -45,25 +44,8 @@ public class SearchService {
         log.debug("Es wurde gesucht nach: {}", search);
 
         return groups.stream()
-                     .filter(group -> group.toString().toLowerCase().contains(search.toLowerCase()))
+                     .filter(group -> group.format().toLowerCase().contains(search.toLowerCase()))
                      .collect(Collectors.toList());
     }
 
-    /**
-     * Sortiert die übergebene Liste an Gruppen, sodass Veranstaltungen am Anfang der Liste sind.
-     *
-     * @param groups Die Liste von Gruppen die sortiert werden soll
-     */
-    private static void sortByGroupType(List<Group> groups) {
-        groups.sort((Group g1, Group g2) -> {
-            if (g1.getType() == Type.LECTURE) {
-                return -1;
-            }
-            if (g2.getType() == Type.LECTURE) {
-                return 0;
-            }
-
-            return 1;
-        });
-    }
 }
diff --git a/src/main/java/mops/gruppen2/persistance/EventRepository.java b/src/main/java/mops/gruppen2/persistance/EventRepository.java
index 6466a77..eaf266e 100644
--- a/src/main/java/mops/gruppen2/persistance/EventRepository.java
+++ b/src/main/java/mops/gruppen2/persistance/EventRepository.java
@@ -30,28 +30,28 @@ public interface EventRepository extends CrudRepository<EventDTO, Long> {
 
     @Query("SELECT * FROM event"
            + " WHERE group_id IN (:userIds) ")
-    List<EventDTO> findEventDTOsByUser(@Param("groupIds") List<String> userIds);
+    List<EventDTO> findEventDTOsByUser(@Param("groupIds") String... userIds);
 
     @Query("SELECT * FROM event"
            + " WHERE event_type IN (:types)")
-    List<EventDTO> findEventDTOsByType(@Param("types") List<String> types);
+    List<EventDTO> findEventDTOsByType(@Param("types") String... types);
 
     @Query("SELECT * FROM event"
            + " WHERE event_type IN (:types) AND group_id IN (:groupIds)")
-    List<EventDTO> findEventDTOsByGroupAndType(@Param("types") List<String> types,
-                                               @Param("groupIds") List<String> groupIds);
+    List<EventDTO> findEventDTOsByGroupAndType(@Param("groupIds") List<String> groupIds,
+                                               @Param("types") String... types);
 
     @Query("SELECT * FROM event"
            + " WHERE event_type IN (:types) AND user_id = :userId")
-    List<EventDTO> findEventDTOsByUserAndType(@Param("types") List<String> types,
-                                              @Param("userId") String userId);
+    List<EventDTO> findEventDTOsByUserAndType(@Param("userId") String userId,
+                                              @Param("types") String... types);
 
     // ################################ LATEST EVENT DTOs ########################################
 
     @Query("WITH ranked_events AS ("
            + "SELECT *, ROW_NUMBER() OVER (PARTITION BY group_id ORDER BY event_id DESC) AS rn"
            + " FROM event"
-           + " WHERE user_id = :userId AND event_type IN ('AddUserEvent', 'DeleteUserEvent')"
+           + " WHERE user_id = :userId AND event_type IN ('ADDMEMBER', 'KICKMEMBER')"
            + ")"
            + "SELECT * FROM ranked_events WHERE rn = 1;")
     List<EventDTO> findLatestEventDTOsPartitionedByGroupByUser(@Param("userId") String userId);
@@ -62,7 +62,7 @@ public interface EventRepository extends CrudRepository<EventDTO, Long> {
            + " WHERE event_type IN (:types)"
            + ")"
            + "SELECT * FROM ranked_events WHERE rn = 1;")
-    List<EventDTO> findLatestEventDTOsPartitionedByGroupByType(@Param("types") List<String> types);
+    List<EventDTO> findLatestEventDTOsPartitionedByGroupByType(@Param("types") String... types);
 
     // ######################################### COUNT ###########################################
 
diff --git a/src/main/java/mops/gruppen2/persistance/InviteRepository.java b/src/main/java/mops/gruppen2/persistance/InviteRepository.java
deleted file mode 100644
index 246a289..0000000
--- a/src/main/java/mops/gruppen2/persistance/InviteRepository.java
+++ /dev/null
@@ -1,22 +0,0 @@
-package mops.gruppen2.persistance;
-
-import mops.gruppen2.persistance.dto.InviteLinkDTO;
-import org.springframework.data.jdbc.repository.query.Modifying;
-import org.springframework.data.jdbc.repository.query.Query;
-import org.springframework.data.repository.CrudRepository;
-import org.springframework.data.repository.query.Param;
-import org.springframework.stereotype.Repository;
-
-@Repository
-public interface InviteRepository extends CrudRepository<InviteLinkDTO, Long> {
-
-    @Query("SELECT group_id FROM invite WHERE invite_link = :link")
-    String findGroupIdByLink(@Param("link") String link);
-
-    @Modifying
-    @Query("DELETE FROM invite WHERE group_id = :group")
-    void deleteLinkOfGroup(@Param("group") String group);
-
-    @Query("SELECT invite_link FROM invite WHERE group_id = :group")
-    String findLinkByGroupId(@Param("group") String group);
-}
diff --git a/src/main/java/mops/gruppen2/persistance/dto/EventDTO.java b/src/main/java/mops/gruppen2/persistance/dto/EventDTO.java
index 832abee..eacbfd1 100644
--- a/src/main/java/mops/gruppen2/persistance/dto/EventDTO.java
+++ b/src/main/java/mops/gruppen2/persistance/dto/EventDTO.java
@@ -12,8 +12,13 @@ public class EventDTO {
 
     @Id
     Long event_id;
+
     String group_id;
-    String user_id;
+    long group_version;
+
+    String exec_user_id;
+    String target_user_id;
+
     String event_type;
     String event_payload;
 }
diff --git a/src/main/java/mops/gruppen2/persistance/dto/InviteLinkDTO.java b/src/main/java/mops/gruppen2/persistance/dto/InviteLinkDTO.java
deleted file mode 100644
index db28e7c..0000000
--- a/src/main/java/mops/gruppen2/persistance/dto/InviteLinkDTO.java
+++ /dev/null
@@ -1,17 +0,0 @@
-package mops.gruppen2.persistance.dto;
-
-import lombok.AllArgsConstructor;
-import lombok.Getter;
-import org.springframework.data.annotation.Id;
-import org.springframework.data.relational.core.mapping.Table;
-
-@Table("invite")
-@Getter
-@AllArgsConstructor
-public class InviteLinkDTO {
-
-    @Id
-    Long invite_id;
-    String group_id;
-    String invite_link;
-}
diff --git a/src/main/java/mops/gruppen2/web/APIController.java b/src/main/java/mops/gruppen2/web/APIController.java
index 75d12d5..38d1432 100644
--- a/src/main/java/mops/gruppen2/web/APIController.java
+++ b/src/main/java/mops/gruppen2/web/APIController.java
@@ -7,9 +7,8 @@ import lombok.RequiredArgsConstructor;
 import lombok.extern.log4j.Log4j2;
 import mops.gruppen2.aspect.annotation.TraceMethodCalls;
 import mops.gruppen2.domain.helper.APIHelper;
-import mops.gruppen2.domain.helper.IdHelper;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.helper.CommonHelper;
+import mops.gruppen2.domain.model.group.Group;
 import mops.gruppen2.domain.service.EventStoreService;
 import mops.gruppen2.domain.service.ProjectionService;
 import mops.gruppen2.web.api.GroupRequestWrapper;
@@ -60,7 +59,7 @@ public class APIController {
     public List<String> getApiUserGroups(@ApiParam("Nutzer-Id")
                                          @PathVariable("id") String userId) {
 
-        return IdHelper.uuidsToString(eventStoreService.findExistingUserGroups(new User(userId)));
+        return CommonHelper.uuidsToString(eventStoreService.findExistingUserGroups(userId));
     }
 
     /**
diff --git a/src/main/java/mops/gruppen2/web/GroupCreationController.java b/src/main/java/mops/gruppen2/web/GroupCreationController.java
index 9cc435c..af56d77 100644
--- a/src/main/java/mops/gruppen2/web/GroupCreationController.java
+++ b/src/main/java/mops/gruppen2/web/GroupCreationController.java
@@ -4,16 +4,16 @@ import lombok.RequiredArgsConstructor;
 import lombok.extern.log4j.Log4j2;
 import mops.gruppen2.aspect.annotation.TraceMethodCalls;
 import mops.gruppen2.domain.helper.CsvHelper;
-import mops.gruppen2.domain.helper.IdHelper;
 import mops.gruppen2.domain.helper.ValidationHelper;
-import mops.gruppen2.domain.model.Description;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Limit;
-import mops.gruppen2.domain.model.Title;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Type;
+import mops.gruppen2.domain.model.group.User;
+import mops.gruppen2.domain.model.group.wrapper.Description;
+import mops.gruppen2.domain.model.group.wrapper.Limit;
+import mops.gruppen2.domain.model.group.wrapper.Parent;
+import mops.gruppen2.domain.model.group.wrapper.Title;
 import mops.gruppen2.domain.service.GroupService;
 import mops.gruppen2.domain.service.ProjectionService;
-import mops.gruppen2.web.form.CreateForm;
 import org.keycloak.adapters.springsecurity.token.KeycloakAuthenticationToken;
 import org.springframework.cache.annotation.CacheEvict;
 import org.springframework.stereotype.Controller;
@@ -21,6 +21,8 @@ import org.springframework.ui.Model;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.multipart.MultipartFile;
 
 import javax.annotation.security.RolesAllowed;
 import javax.validation.Valid;
@@ -49,27 +51,27 @@ public class GroupCreationController {
     @PostMapping("/create")
     @CacheEvict(value = "groups", allEntries = true)
     public String postCreateOrga(KeycloakAuthenticationToken token,
-                                 @Valid CreateForm create,
-                                 @Valid Title title,
-                                 @Valid Description description,
-                                 @Valid Limit limit) {
+                                 @RequestParam("type") Type type,
+                                 @RequestParam("parent") @Valid Parent parent,
+                                 @RequestParam("title") @Valid Title title,
+                                 @RequestParam("description") @Valid Description description,
+                                 @RequestParam("limit") @Valid Limit limit,
+                                 @RequestParam(value = "file", required = false) MultipartFile file) {
 
         // Zusätzlicher check: studentin kann keine lecture erstellen
-        ValidationHelper.validateCreateForm(token, create);
+        ValidationHelper.validateCreateForm(token, type);
 
-        User user = new User(token);
-        Group group = groupService.createGroup(user,
-                                               title,
-                                               description,
-                                               create.getType(),
-                                               limit,
-                                               create.getParent());
+        String principal = token.getName();
+        Group group = groupService.createGroup(principal);
+        groupService.initGroupMembers(group, principal, principal, new User(token), limit);
+        groupService.initGroupMeta(group, principal, type, parent);
+        groupService.initGroupText(group, principal, title, description);
 
         // ROLE_studentin kann kein CSV importieren
         if (token.getAccount().getRoles().contains("orga")) {
-            groupService.addUsersToGroup(CsvHelper.readCsvFile(create.getFile()), group, user);
+            groupService.addUsersToGroup(group, principal, CsvHelper.readCsvFile(file));
         }
 
-        return "redirect:/gruppen2/details/" + IdHelper.uuidToString(group.getGroupid());
+        return "redirect:/gruppen2/details/" + group.getId();
     }
 }
diff --git a/src/main/java/mops/gruppen2/web/GroupDetailsController.java b/src/main/java/mops/gruppen2/web/GroupDetailsController.java
index 843cba1..eafb33c 100644
--- a/src/main/java/mops/gruppen2/web/GroupDetailsController.java
+++ b/src/main/java/mops/gruppen2/web/GroupDetailsController.java
@@ -4,15 +4,13 @@ import lombok.RequiredArgsConstructor;
 import lombok.extern.log4j.Log4j2;
 import mops.gruppen2.aspect.annotation.TraceMethodCalls;
 import mops.gruppen2.domain.helper.CsvHelper;
-import mops.gruppen2.domain.helper.IdHelper;
 import mops.gruppen2.domain.helper.ValidationHelper;
-import mops.gruppen2.domain.model.Description;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Limit;
-import mops.gruppen2.domain.model.Title;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.User;
+import mops.gruppen2.domain.model.group.wrapper.Description;
+import mops.gruppen2.domain.model.group.wrapper.Limit;
+import mops.gruppen2.domain.model.group.wrapper.Title;
 import mops.gruppen2.domain.service.GroupService;
-import mops.gruppen2.domain.service.InviteService;
 import mops.gruppen2.domain.service.ProjectionService;
 import org.keycloak.adapters.springsecurity.token.KeycloakAuthenticationToken;
 import org.springframework.cache.annotation.CacheEvict;
@@ -38,7 +36,6 @@ import java.util.UUID;
 @RequestMapping("/gruppen2")
 public class GroupDetailsController {
 
-    private final InviteService inviteService;
     private final GroupService groupService;
     private final ProjectionService projectionService;
 
@@ -48,18 +45,17 @@ public class GroupDetailsController {
                                  Model model,
                                  @PathVariable("id") String groupId) {
 
-        User user = new User(token);
+        String principal = token.getName();
         Group group = projectionService.projectSingleGroup(UUID.fromString(groupId));
 
         // Parent Badge
-        UUID parentId = group.getParent();
-        Group parent = projectionService.projectParent(parentId);
+        Group parent = projectionService.projectParent(group.getParent());
 
         model.addAttribute("group", group);
         model.addAttribute("parent", parent);
 
         // Detailseite für nicht-Mitglieder
-        if (!ValidationHelper.checkIfMember(group, user)) {
+        if (!ValidationHelper.checkIfMember(group, principal)) {
             return "preview";
         }
 
@@ -72,14 +68,14 @@ public class GroupDetailsController {
     public String postDetailsJoin(KeycloakAuthenticationToken token,
                                   @PathVariable("id") String groupId) {
 
-        User user = new User(token);
+        String principal = token.getName();
         Group group = projectionService.projectSingleGroup(UUID.fromString(groupId));
 
-        if (ValidationHelper.checkIfMember(group, user)) {
+        if (ValidationHelper.checkIfMember(group, principal)) {
             return "redirect:/gruppen2/details/" + groupId;
         }
 
-        groupService.addUser(user, group);
+        groupService.addMember(group, principal, principal, new User(token));
 
         return "redirect:/gruppen2/details/" + groupId;
     }
@@ -90,12 +86,10 @@ public class GroupDetailsController {
     public String postDetailsLeave(KeycloakAuthenticationToken token,
                                    @PathVariable("id") String groupId) {
 
-        User user = new User(token);
+        String principal = token.getName();
         Group group = projectionService.projectSingleGroup(UUID.fromString(groupId));
 
-        ValidationHelper.throwIfNoMember(group, user);
-
-        groupService.deleteUser(user, group);
+        groupService.deleteUser(group, principal, principal);
 
         return "redirect:/gruppen2";
     }
@@ -107,15 +101,15 @@ public class GroupDetailsController {
                                  HttpServletRequest request,
                                  @PathVariable("id") String groupId) {
 
-        User user = new User(token);
+        String principal = token.getName();
         Group group = projectionService.projectSingleGroup(UUID.fromString(groupId));
 
         // Invite Link
         String actualURL = request.getRequestURL().toString();
         String serverURL = actualURL.substring(0, actualURL.indexOf("gruppen2/"));
-        String link = serverURL + "gruppen2/join/" + inviteService.getLinkByGroup(group);
+        String link = serverURL + "gruppen2/join/" + group.getLink();
 
-        ValidationHelper.throwIfNoAdmin(group, user);
+        ValidationHelper.throwIfNoAdmin(group, principal);
 
         model.addAttribute("group", group);
         model.addAttribute("link", link);
@@ -131,11 +125,11 @@ public class GroupDetailsController {
                                       @Valid Title title,
                                       @Valid Description description) {
 
-        User user = new User(token);
+        String principal = token.getName();
         Group group = projectionService.projectSingleGroup(UUID.fromString(groupId));
 
-        groupService.updateTitle(user, group, title);
-        groupService.updateDescription(user, group, description);
+        groupService.setTitle(group, principal, title);
+        groupService.setDescription(group, principal, description);
 
         return "redirect:/gruppen2/details/" + groupId + "/edit";
     }
@@ -146,10 +140,10 @@ public class GroupDetailsController {
     public String postDetailsEditUserLimit(KeycloakAuthenticationToken token,
                                            @PathVariable("id") String groupId,
                                            @Valid Limit limit) {
-        User user = new User(token);
+        String principal = token.getName();
         Group group = projectionService.projectSingleGroup(UUID.fromString(groupId));
 
-        groupService.updateUserLimit(user, group, limit);
+        groupService.setLimit(group, principal, limit);
 
         return "redirect:/gruppen2/details/" + groupId + "/edit";
     }
@@ -161,10 +155,10 @@ public class GroupDetailsController {
                                      @PathVariable("id") String groupId,
                                      @RequestParam(value = "file", required = false) MultipartFile file) {
 
-        User user = new User(token);
-        Group group = projectionService.projectSingleGroup(IdHelper.stringToUUID(groupId));
+        String principal = token.getName();
+        Group group = projectionService.projectSingleGroup(UUID.fromString(groupId));
 
-        groupService.addUsersToGroup(CsvHelper.readCsvFile(file), group, user);
+        groupService.addUsersToGroup(group, principal, CsvHelper.readCsvFile(file));
 
         return "redirect:/gruppen2/details/" + groupId + "/edit";
     }
@@ -174,17 +168,17 @@ public class GroupDetailsController {
     @CacheEvict(value = "groups", allEntries = true)
     public String postDetailsEditRole(KeycloakAuthenticationToken token,
                                       @PathVariable("id") String groupId,
-                                      @PathVariable("userid") String userId) {
+                                      @PathVariable("userid") String target) {
 
-        User user = new User(token);
+        String principal = token.getName();
         Group group = projectionService.projectSingleGroup(UUID.fromString(groupId));
 
-        ValidationHelper.throwIfNoAdmin(group, user);
+        ValidationHelper.throwIfNoAdmin(group, principal);
 
-        groupService.toggleMemberRole(new User(userId), group);
+        groupService.toggleMemberRole(group, principal, target);
 
         // Falls sich der User selbst die Rechte genommen hat
-        if (!ValidationHelper.checkIfAdmin(group, user)) {
+        if (!ValidationHelper.checkIfAdmin(group, principal)) {
             return "redirect:/gruppen2/details/" + groupId;
         }
 
@@ -196,16 +190,16 @@ public class GroupDetailsController {
     @CacheEvict(value = "groups", allEntries = true)
     public String postDetailsEditDelete(KeycloakAuthenticationToken token,
                                         @PathVariable("id") String groupId,
-                                        @PathVariable("userid") String userId) {
+                                        @PathVariable("userid") String target) {
 
-        User user = new User(token);
+        String principal = token.getName();
         Group group = projectionService.projectSingleGroup(UUID.fromString(groupId));
 
-        ValidationHelper.throwIfNoAdmin(group, user);
+        ValidationHelper.throwIfNoAdmin(group, principal);
 
         // Der eingeloggte User kann sich nicht selbst entfernen (er kann aber verlassen)
-        if (!userId.equals(user.getUserid())) {
-            groupService.deleteUser(new User(userId), group);
+        if (!principal.equals(target)) {
+            groupService.deleteUser(group, principal, target);
         }
 
         return "redirect:/gruppen2/details/" + groupId + "/edit";
@@ -215,12 +209,12 @@ public class GroupDetailsController {
     @PostMapping("/details/{id}/edit/destroy")
     @CacheEvict(value = "groups", allEntries = true)
     public String postDetailsEditDestroy(KeycloakAuthenticationToken token,
-                                         @PathVariable("id") String groupId) {
+                                         @PathVariable("id") String groupid) {
 
-        User user = new User(token);
-        Group group = projectionService.projectSingleGroup(UUID.fromString(groupId));
+        String principal = token.getName();
+        Group group = projectionService.projectSingleGroup(UUID.fromString(groupid));
 
-        groupService.deleteGroup(user, group);
+        groupService.deleteGroup(group, principal);
 
         return "redirect:/gruppen2";
     }
diff --git a/src/main/java/mops/gruppen2/web/GruppenfindungController.java b/src/main/java/mops/gruppen2/web/GruppenfindungController.java
index 96f1048..465be52 100644
--- a/src/main/java/mops/gruppen2/web/GruppenfindungController.java
+++ b/src/main/java/mops/gruppen2/web/GruppenfindungController.java
@@ -4,7 +4,6 @@ import lombok.RequiredArgsConstructor;
 import lombok.extern.log4j.Log4j2;
 import mops.gruppen2.aspect.annotation.TraceMethodCall;
 import mops.gruppen2.domain.exception.PageNotFoundException;
-import mops.gruppen2.domain.model.User;
 import mops.gruppen2.domain.service.ProjectionService;
 import org.keycloak.adapters.springsecurity.token.KeycloakAuthenticationToken;
 import org.springframework.stereotype.Controller;
@@ -35,9 +34,8 @@ public class GruppenfindungController {
     public String getIndexPage(KeycloakAuthenticationToken token,
                                Model model) {
 
-        User user = new User(token);
-
-        model.addAttribute("groups", projectionService.projectUserGroups(user));
+        String principal = token.getName();
+        model.addAttribute("groups", projectionService.projectUserGroups(principal));
 
         return "index";
     }
diff --git a/src/main/java/mops/gruppen2/web/ModelAttributeControllerAdvice.java b/src/main/java/mops/gruppen2/web/ModelAttributeControllerAdvice.java
index 364a189..71c432f 100644
--- a/src/main/java/mops/gruppen2/web/ModelAttributeControllerAdvice.java
+++ b/src/main/java/mops/gruppen2/web/ModelAttributeControllerAdvice.java
@@ -1,9 +1,9 @@
 package mops.gruppen2.web;
 
 import mops.gruppen2.domain.Account;
-import mops.gruppen2.domain.model.Role;
-import mops.gruppen2.domain.model.Type;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.model.group.Role;
+import mops.gruppen2.domain.model.group.Type;
+import mops.gruppen2.domain.model.group.User;
 import org.keycloak.adapters.springsecurity.token.KeycloakAuthenticationToken;
 import org.springframework.ui.Model;
 import org.springframework.web.bind.annotation.ControllerAdvice;
@@ -20,15 +20,15 @@ public class ModelAttributeControllerAdvice {
         // Prevent NullPointerException if not logged in
         if (token != null) {
             model.addAttribute("account", new Account(token));
-            model.addAttribute("user", new User(token));
+            model.addAttribute("principal", new User(token));
         }
 
         // Add enums
-        model.addAttribute("member", Role.MEMBER);
-        model.addAttribute("admin", Role.ADMIN);
-        model.addAttribute("public", Type.PUBLIC);
-        model.addAttribute("private", Type.PRIVATE);
-        model.addAttribute("lecture", Type.LECTURE);
+        model.addAttribute("REGULAR", Role.REGULAR);
+        model.addAttribute("ADMIN", Role.ADMIN);
+        model.addAttribute("PUBLIC", Type.PUBLIC);
+        model.addAttribute("PRIVATE", Type.PRIVATE);
+        model.addAttribute("LECTURE", Type.LECTURE);
     }
 
 }
diff --git a/src/main/java/mops/gruppen2/web/SearchAndInviteController.java b/src/main/java/mops/gruppen2/web/SearchAndInviteController.java
index db51f2c..10bc6f6 100644
--- a/src/main/java/mops/gruppen2/web/SearchAndInviteController.java
+++ b/src/main/java/mops/gruppen2/web/SearchAndInviteController.java
@@ -4,10 +4,8 @@ import lombok.RequiredArgsConstructor;
 import lombok.extern.log4j.Log4j2;
 import mops.gruppen2.aspect.annotation.TraceMethodCalls;
 import mops.gruppen2.domain.helper.ValidationHelper;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Type;
-import mops.gruppen2.domain.model.User;
-import mops.gruppen2.domain.service.InviteService;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Type;
 import mops.gruppen2.domain.service.ProjectionService;
 import mops.gruppen2.domain.service.SearchService;
 import org.keycloak.adapters.springsecurity.token.KeycloakAuthenticationToken;
@@ -31,7 +29,6 @@ import java.util.List;
 @RequestMapping("/gruppen2")
 public class SearchAndInviteController {
 
-    private final InviteService inviteService;
     private final ProjectionService projectionService;
     private final SearchService searchService;
 
@@ -50,8 +47,8 @@ public class SearchAndInviteController {
                              Model model,
                              @RequestParam("string") String search) {
 
-        User user = new User(token);
-        List<Group> groups = searchService.searchPublicGroups(search, user);
+        String principal = token.getName();
+        List<Group> groups = searchService.searchPublicGroups(search, principal);
 
         model.addAttribute("groups", groups);
 
@@ -64,19 +61,19 @@ public class SearchAndInviteController {
                           Model model,
                           @PathVariable("link") String link) {
 
-        User user = new User(token);
-        Group group = projectionService.projectSingleGroup(inviteService.getGroupIdFromLink(link));
+        String principal = token.getName();
+        Group group = projectionService.projectGroupByLink(link);
 
         model.addAttribute("group", group);
 
         // Gruppe öffentlich
         if (group.getType() == Type.PUBLIC) {
-            return "redirect:/gruppen2/details/" + group.getGroupid();
+            return "redirect:/gruppen2/details/" + group.getId();
         }
 
         // Bereits Mitglied
-        if (ValidationHelper.checkIfMember(group, user)) {
-            return "redirect:/gruppen2/details/" + group.getGroupid();
+        if (ValidationHelper.checkIfMember(group, principal)) {
+            return "redirect:/gruppen2/details/" + group.getId();
         }
 
         return "link";
diff --git a/src/main/java/mops/gruppen2/web/api/GroupRequestWrapper.java b/src/main/java/mops/gruppen2/web/api/GroupRequestWrapper.java
index 73a045b..d8e0680 100644
--- a/src/main/java/mops/gruppen2/web/api/GroupRequestWrapper.java
+++ b/src/main/java/mops/gruppen2/web/api/GroupRequestWrapper.java
@@ -2,7 +2,7 @@ package mops.gruppen2.web.api;
 
 import lombok.AllArgsConstructor;
 import lombok.Getter;
-import mops.gruppen2.domain.model.Group;
+import mops.gruppen2.domain.model.group.Group;
 
 import java.util.List;
 
diff --git a/src/main/java/mops/gruppen2/web/form/CreateForm.java b/src/main/java/mops/gruppen2/web/form/CreateForm.java
deleted file mode 100644
index b5be8b3..0000000
--- a/src/main/java/mops/gruppen2/web/form/CreateForm.java
+++ /dev/null
@@ -1,29 +0,0 @@
-package mops.gruppen2.web.form;
-
-import lombok.Data;
-import mops.gruppen2.domain.helper.IdHelper;
-import mops.gruppen2.domain.model.Type;
-import org.springframework.web.multipart.MultipartFile;
-
-import javax.validation.constraints.NotBlank;
-import java.util.UUID;
-
-@Data
-public class CreateForm {
-
-    @NotBlank
-    String type;
-
-    @NotBlank
-    String parent;
-
-    MultipartFile file;
-
-    public Type getType() {
-        return Type.valueOf(type);
-    }
-
-    public UUID getParent() {
-        return getType() == Type.LECTURE ? IdHelper.emptyUUID() : IdHelper.stringToUUID(parent);
-    }
-}
diff --git a/src/main/resources/application-docker.properties b/src/main/resources/application-docker.properties
index 1b12d91..fb46f63 100644
--- a/src/main/resources/application-docker.properties
+++ b/src/main/resources/application-docker.properties
@@ -2,7 +2,7 @@
 logging.application.name                    = gruppen2
 logging.pattern.console                     = [${logging.application.name}], %magenta(%-5level), %d{dd-MM-yyyy HH:mm:ss.SSS},\t%blue(%msg)\t%thread,%logger.%M%n
 spring.output.ansi.enabled                  = always
-logging.level.mops.gruppen2                 = info
+logging.level.mops.gruppen2                 = trace
 logging.level.org.springframework.jdbc.core = info
 
 # Database
diff --git a/src/main/resources/schema-h2.sql b/src/main/resources/schema-h2.sql
index 72405f2..15e1d44 100644
--- a/src/main/resources/schema-h2.sql
+++ b/src/main/resources/schema-h2.sql
@@ -2,18 +2,11 @@ DROP TABLE IF EXISTS event;
 
 CREATE TABLE event
 (
-    event_id      INT PRIMARY KEY AUTO_INCREMENT,
-    group_id      VARCHAR(36) NOT NULL,
-    user_id       VARCHAR(50),
-    event_type    VARCHAR(32),
-    event_payload VARCHAR(2500)
-);
-
-DROP TABLE IF EXISTS invite;
-
-CREATE TABLE invite
-(
-    invite_id   INT PRIMARY KEY AUTO_INCREMENT,
-    group_id    VARCHAR(36) NOT NULL,
-    invite_link VARCHAR(36) NOT NULL
+    event_id       INT PRIMARY KEY AUTO_INCREMENT,
+    group_id       VARCHAR(36)   NOT NULL,
+    group_version  INT           NOT NULL,
+    exec_user_id   VARCHAR(50)   NOT NULL,
+    target_user_id VARCHAR(50),
+    event_type     VARCHAR(32)   NOT NULL,
+    event_payload  VARCHAR(2500) NOT NULL
 );
diff --git a/src/main/resources/templates/details.html b/src/main/resources/templates/details.html
index 5bf76fc..c9a81b4 100644
--- a/src/main/resources/templates/details.html
+++ b/src/main/resources/templates/details.html
@@ -27,7 +27,7 @@
                         <!--Spacer-->
                         <span class="col"></span>
 
-                        <form method="post" th:action="@{/gruppen2/details/{id}/leave(id=${group.getGroupid()})}">
+                        <form method="post" th:action="@{/gruppen2/details/{id}/leave(id=${group.getId()})}">
                             <button class="btn btn-danger btn-bar" type="submit">Gruppe verlassen
                             </button>
                         </form>
@@ -40,13 +40,13 @@
                 <!--Anzahl Text-->
                 <div class="mb-2">
                     <span>Teilnehmer: </span>
-                    <span th:text="${group.getMembers().size() + ' von ' + group.getLimit().getUserLimit()}"></span>
+                    <span th:text="${group.size() + ' von ' + group.getLimit()}"></span>
                 </div>
 
                 <!--Bearbeiten-Button-->
-                <div class="mb-2" th:if="${group.getRoles().get(user.getUserid()) == admin}">
+                <div class="mb-2" th:if="${group.isAdmin(user.getId())}">
                     <form method="get"
-                          th:action="@{/gruppen2/details/{id}/edit(id=${group.getGroupid()})}">
+                          th:action="@{/gruppen2/details/{id}/edit(id=${group.getId()})}">
                         <button class="btn btn-secondary btn-block">Gruppe verwalten</button>
                     </form>
                 </div>
@@ -55,8 +55,8 @@
                 <div class="members">
                     <ul class="list-group">
                         <li class="list-group-item d-flex justify-content-between"
-                            th:each="member : ${group.getMembers().values()}">
-                            <span th:text="${member.getGivenname()  + ' ' + member.getFamilyname().charAt(0) + '.'}"></span>
+                            th:each="member : ${group.getMembers()}">
+                            <span th:text="${member}"></span>
                             <span th:replace="~{fragments/groups :: userbadges}"></span>
                         </li>
                     </ul>
diff --git a/src/main/resources/templates/edit.html b/src/main/resources/templates/edit.html
index fa04b00..17baeaa 100644
--- a/src/main/resources/templates/edit.html
+++ b/src/main/resources/templates/edit.html
@@ -15,14 +15,14 @@
         <!--Fertig oder löschen-->
         <div class="content">
             <div class="row">
-                <form method="get" th:action="@{/gruppen2/details/{id}(id=${group.getGroupid()})}">
+                <form method="get" th:action="@{/gruppen2/details/{id}(id=${group.getId()})}">
                     <button class="btn btn-primary">Fertig</button>
                 </form>
 
                 <!--Spacer-->
                 <span class="col"></span>
 
-                <form method="post" th:action="@{/gruppen2/details/{id}/edit/destroy(id=${group.getGroupid()})}">
+                <form method="post" th:action="@{/gruppen2/details/{id}/edit/destroy(id=${group.getId()})}">
                     <button class="btn btn-danger btn-bar" type="submit">Gruppe löschen
                     </button>
                 </form>
@@ -50,7 +50,7 @@
 
             <!--Beschreibung + Titel-->
             <div class="content-text">
-                <form th:action="@{/gruppen2/details/{id}/edit/meta(id=${group.getGroupid()})}"
+                <form th:action="@{/gruppen2/details/{id}/edit/meta(id=${group.getId()})}"
                       method="post">
 
                     <div th:replace="~{fragments/forms :: meta}"></div>
@@ -63,7 +63,7 @@
 
             <!--Userlimit-->
             <div class="content-text-in">
-                <form th:action="@{/gruppen2/details/{id}/edit/userlimit(id=${group.getGroupid()})}"
+                <form th:action="@{/gruppen2/details/{id}/edit/userlimit(id=${group.getId()})}"
                       method="post">
 
                     <div th:replace="~{fragments/forms :: userlimit}"></div>
@@ -76,7 +76,7 @@
 
             <!--CSV Import-->
             <div class="content-text mb-0">
-                <form th:action="@{/gruppen2/details/{id}/edit/csv(id=${group.getGroupid()})}"
+                <form th:action="@{/gruppen2/details/{id}/edit/csv(id=${group.getId()})}"
                       th:if="${account.getRoles().contains('orga')}"
                       enctype="multipart/form-data" method="post">
 
@@ -96,20 +96,20 @@
             </div>
 
             <ul class="list-group">
-                <li class="list-group-item d-flex justify-content-between" th:each="member : ${group.getMembers().values()}">
+                <li class="list-group-item d-flex justify-content-between" th:each="member : ${group.getMembers()}">
                     <div>
                         <span th:text="${member.getGivenname()  + ' ' + member.getFamilyname().charAt(0) + '.'}"></span>
                         <span th:replace="~{fragments/groups :: userbadges}"></span>
                     </div>
 
                     <div class="d-flex">
-                        <form th:action="@{/gruppen2/details/{id}/edit/delete/{userid}(id=${group.getGroupid()}, userid=${member.getUserid()})}"
-                              th:unless="${member.getUserid() == account.getName()}"
+                        <form th:action="@{/gruppen2/details/{id}/edit/delete/{userid}(id=${group.getId()}, userid=${member.getId()})}"
+                              th:unless="${member.getId() == account.getName()}"
                               method="post">
                             <button type="submit" class="btn btn-danger mr-2">Entfernen</button>
                         </form>
 
-                        <form th:action="@{/gruppen2/details/{id}/edit/role/{userid}(id=${group.getGroupid()}, userid=${member.getUserid()})}"
+                        <form th:action="@{/gruppen2/details/{id}/edit/role/{userid}(id=${group.getId()}, userid=${member.getId()})}"
                               method="post">
                             <button type="submit" class="btn btn-warning">Rolle ändern</button>
                         </form>
diff --git a/src/main/resources/templates/fragments/forms.html b/src/main/resources/templates/fragments/forms.html
index ba4a19a..d8b539b 100644
--- a/src/main/resources/templates/fragments/forms.html
+++ b/src/main/resources/templates/fragments/forms.html
@@ -10,7 +10,7 @@
         <div class="input-group-prepend">
             <span class="input-group-text text-monospace">Gruppentitel:</span>
         </div>
-        <input type="text" class="form-control" name="groupTitle" minlength="4" maxlength="128"
+        <input type="text" class="form-control" name="title" minlength="4" maxlength="128"
                th:value="${group?.getTitle()}" required>
     </div>
 
@@ -20,8 +20,8 @@
         <div class="input-group-prepend">
             <span class="input-group-text text-monospace">Beschreibung:</span>
         </div>
-        <textarea class="form-control" name="groupDescription" minlength="4" maxlength="512"
-                  th:text="${group?.getDescription()?.getGroupDescription()}" required></textarea>
+        <textarea class="form-control" name="description" minlength="4" maxlength="512"
+                  th:text="${group?.getDescription()}" required></textarea>
     </div>
 </th:block>
 
@@ -50,7 +50,7 @@
             <input type="hidden" id="parentdummy" name="parent" value="00000000-0000-0000-0000-000000000000" disabled>
             <select class="custom-select" id="parentselect" name="parent">
                 <option value="00000000-0000-0000-0000-000000000000" selected>Keiner</option>
-                <option th:each="lecture : ${lectures}" th:value="${lecture.getGroupid()}"
+                <option th:each="lecture : ${lectures}" th:value="${lecture.getId()}"
                         th:text="${lecture.getTitle()}"></option>
             </select>
         </div>
@@ -61,17 +61,17 @@
 <th:block th:fragment="userlimit">
     <label for="userlimit">Teilnehmeranzahl:</label>
     <div class="btn-toolbar row mx-0" id="userlimit">
-        <input type="hidden" name="userLimit" id="limit" value="999999"
-               th:disabled="${group != null && group.getLimit().getUserLimit() < 999999} ? 'disabled' : 'false'">
+        <input type="hidden" name="limit" id="limit" value="999999"
+               th:disabled="${group != null && group.getLimit() < 999999} ? 'disabled' : 'false'">
         <div class="btn-group btn-group-toggle col-sm-4 px-0" data-toggle="buttons">
             <label class="btn btn-secondary active" onclick="disable('#limitselect'); enable('#limit')">
                 <input type="radio"
-                       th:checked="${group != null && group.getLimit().getUserLimit() < 999999} ? 'false' : 'checked'">
+                       th:checked="${group != null && group.getLimit() < 999999} ? 'false' : 'checked'">
                 Unbegrenzt
             </label>
             <label class="btn btn-secondary" onclick="enable('#limitselect'); disable('#limit')">
                 <input type="radio"
-                       th:checked="${group != null && group.getLimit().getUserLimit() < 999999} ? 'checked' : 'false'">
+                       th:checked="${group != null && group.getLimit() < 999999} ? 'checked' : 'false'">
                 Begrenzt
             </label>
         </div>
@@ -81,10 +81,10 @@
             <div class="input-group-prepend">
                 <span class="input-group-text text-monospace">Limit:</span>
             </div>
-            <input type="number" class="form-control" name="userLimit"
-                   th:value="${group != null} ? ${group.getLimit().getUserLimit()} : '999999'"
+            <input type="number" class="form-control" name="limit"
+                   th:value="${group != null} ? ${group.getLimit()} : '999999'"
                    min="1" max="999999" id="limitselect" required
-                   th:disabled="${group != null && group.getLimit().getUserLimit() < 999999} ? 'false' : 'disabled'">
+                   th:disabled="${group != null && group.getLimit() < 999999} ? 'false' : 'disabled'">
             <div class="input-group-append">
                 <span class="input-group-text text-monospace">Teilnehmer</span>
             </div>
@@ -99,7 +99,7 @@
         <span class="input-group-text text-monospace">CSV:</span>
     </div>
     <div class="custom-file">
-        <input type="file" class="custom-file-input" id="file" th:name="file">
+        <input type="file" class="custom-file-input" id="file" name="file">
         <label class="custom-file-label" for="file">Datei auswählen</label>
     </div>
     <script>
diff --git a/src/main/resources/templates/fragments/groups.html b/src/main/resources/templates/fragments/groups.html
index adcd03d..921ca9b 100644
--- a/src/main/resources/templates/fragments/groups.html
+++ b/src/main/resources/templates/fragments/groups.html
@@ -1,21 +1,20 @@
 <!DOCTYPE HTML>
-<!--suppress ALL -->
 <html lang="de" xmlns:th="http://www.thymeleaf.org">
 
 <!--Grouptype Badges-->
 <th:block th:fragment="badges">
     <span class="badge badge-pill private"
           title="Kann nicht über die Suche gefunden werden, beitritt ist per Einladungslink möglich."
-          th:if='${group.getType() == private}'>Privat</span>
+          th:if='${group.isPrivate()}'>Privat</span>
     <span class="badge badge-pill public"
           title="Kann über die Suche gefunden werden, jeder kann beitreten."
-          th:if="${group.getType() == public}">Öffentlich</span>
+          th:if="${group.isPublic()}">Öffentlich</span>
     <span class="badge badge-pill lecture"
           title="Offizielle Veranstaltung"
-          th:if='${group.getType() == lecture}'>Veranstaltung</span>
+          th:if='${group.isLecture()}'>Veranstaltung</span>
 
     <span class="badge badge-pill parent"
-          th:unless="${parent == null || parent?.getTitle() == null|| parent?.getTitle() == ''}"
+          th:if="${parent != null && parent?.getTitle() != null && parent?.getTitle() != ''}"
           th:title="${'Die Gruppe gehört zur Veranstaltung ' + parent.getTitle() + '.'}"
           th:text="${parent.getTitle()}">Parent</span>
 
@@ -28,7 +27,7 @@
 <!--User Badges-->
 <th:block th:fragment="userbadges">
     <span class="badge badge-success align-self-start ml-2"
-          th:if="${group.getRoles().get(member.getUserid()) == admin}">Admin</span>
+          th:if="${group.isAdmin(member.getUserid())}">Admin</span>
 </th:block>
 
 <th:block th:fragment="groupcontent">
@@ -39,30 +38,30 @@
 
     <!--Description-->
     <div class="content-text-in">
-        <span th:text="${group.getDescription().getGroupDescription()}"></span>
+        <span th:text="${group.getDescription()}"></span>
     </div>
 
-    <!--<div class="content-text-in" th:if="${group.getMembers().contains(user.getId())}"></div>-->
+    <!--<div class="body-text-in" th:if="${group.getMembers().contains(user.getId())}"></div>-->
 </th:block>
 
 <!--Buttonbar zum Gruppe beitreten-->
 <th:block th:fragment="joingroup">
     <div class="content-heading">
-        <span th:if="${group.getMembers().size() < group.getLimit().getUserLimit()}">
+        <span th:unless="${group.isFull()}">
             Möchtest du dieser Gruppe beitreten?
         </span>
-        <span th:unless="${group.getMembers().size() < group.getLimit().getUserLimit()}">
+        <span th:if="${group.isFull()}">
             Diese Gruppe hat ihre maximale Teilnehmeranzahl erreicht.
         </span>
     </div>
 
     <div class="row">
         <form method="post" th:action="@{/gruppen2/details/{id}/join(id = ${group.getGroupId()})}"
-              th:if="${group.getMembers().size() < group.getLimit().getUserLimit()}">
+              th:unless="${group.isFull()}">
             <button class="btn btn-success" type="submit">Gruppe beitreten.</button>
         </form>
 
-        <div class="col" th:if="${group.getMembers().size() < group.getLimit().getUserLimit()}"></div>
+        <div class="col" th:unless="${group.isFull()}"></div>
 
         <a class="btn btn-primary" href="/gruppen2"
            type="submit">Startseite.</a>
diff --git a/src/main/resources/templates/index.html b/src/main/resources/templates/index.html
index 7fb5c52..5a3ef98 100644
--- a/src/main/resources/templates/index.html
+++ b/src/main/resources/templates/index.html
@@ -16,13 +16,13 @@
         <!--Gruppenliste belegte Gruppen-->
         <div class="content" th:each="group: ${groups}">
             <div class="content-heading row">
-                <a class="link col" th:href="@{/gruppen2/details/{id}(id=${group.getGroupid()})}"
+                <a class="link col" th:href="@{/gruppen2/details/{id}(id=${group.getId()})}"
                    th:text="${group.getTitle()}"></a>
 
                 <span th:replace="~{fragments/groups :: badges}"></span>
             </div>
             <div class="content-text-in">
-                <span th:text="${group.getDescription().getGroupDescription()}"></span>
+                <span th:text="${group.getDescription()}"></span>
             </div>
         </div>
 
diff --git a/src/main/resources/templates/preview.html b/src/main/resources/templates/preview.html
index 8f8af66..94b6ea0 100644
--- a/src/main/resources/templates/preview.html
+++ b/src/main/resources/templates/preview.html
@@ -14,10 +14,10 @@
 
         <div class="content" th:insert="~{fragments/groups :: groupcontent}"></div>
 
-        <div class="content" th:unless="${group.getType() == private}"
+        <div class="content" th:unless="${group.isPrivate()}"
              th:insert="~{fragments/groups :: joingroup}"></div>
 
-        <div class="content row" th:if="${group.getType() == private}">
+        <div class="content row" th:if="${group.isPrivate()}">
             <span class="col"></span>
 
             <a class="btn btn-primary" href="/gruppen2">Startseite.</a>
diff --git a/src/main/resources/templates/search.html b/src/main/resources/templates/search.html
index 21dcd4d..132d82d 100644
--- a/src/main/resources/templates/search.html
+++ b/src/main/resources/templates/search.html
@@ -31,11 +31,11 @@
             <div class="content-heading row">
                 <span th:replace="~{fragments/groups :: badges}"></span>
 
-                <a class="link col" th:href="@{/gruppen2/details/{id}(id=${group.getGroupid()})}"
+                <a class="link col" th:href="@{/gruppen2/details/{id}(id=${group.getId()})}"
                    th:text="${group.getTitle()}"></a>
             </div>
             <div class="content-text-in">
-                <span th:text="${group.getDescription().getGroupDescription()}"></span>
+                <span th:text="${group.getDescription()}"></span>
             </div>
         </div>
 
diff --git a/src/test/java/mops/gruppen2/TestBuilder.java b/src/test/java/mops/gruppen2/TestBuilder.java
index 3ac61d7..f723d2b 100644
--- a/src/test/java/mops/gruppen2/TestBuilder.java
+++ b/src/test/java/mops/gruppen2/TestBuilder.java
@@ -2,18 +2,17 @@ package mops.gruppen2;
 
 import com.github.javafaker.Faker;
 import mops.gruppen2.domain.Account;
-import mops.gruppen2.domain.event.AddUserEvent;
-import mops.gruppen2.domain.event.CreateGroupEvent;
-import mops.gruppen2.domain.event.DeleteGroupEvent;
-import mops.gruppen2.domain.event.DeleteUserEvent;
+import mops.gruppen2.domain.event.AddMemberEvent;
+import mops.gruppen2.domain.event.DestroyGroupEvent;
 import mops.gruppen2.domain.event.Event;
-import mops.gruppen2.domain.event.UpdateGroupDescriptionEvent;
-import mops.gruppen2.domain.event.UpdateGroupTitleEvent;
+import mops.gruppen2.domain.event.KickMemberEvent;
+import mops.gruppen2.domain.event.SetDescriptionEvent;
+import mops.gruppen2.domain.event.SetLimitEvent;
+import mops.gruppen2.domain.event.SetTitleEvent;
 import mops.gruppen2.domain.event.UpdateRoleEvent;
-import mops.gruppen2.domain.event.UpdateUserLimitEvent;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Role;
-import mops.gruppen2.domain.model.Type;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Role;
+import mops.gruppen2.domain.model.group.Type;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -93,7 +92,7 @@ public class TestBuilder {
         eventList.add(createPublicGroupEvent(groupId));
         eventList.add(updateGroupTitleEvent(groupId));
         eventList.add(updateGroupDescriptionEvent(groupId));
-        eventList.add(new UpdateUserLimitEvent(groupId, "fgsadggas", Long.MAX_VALUE));
+        eventList.add(new SetLimitEvent(groupId, "fgsadggas", Long.MAX_VALUE));
         eventList.addAll(addUserEvents(membercount, groupId));
 
         return eventList;
@@ -106,7 +105,7 @@ public class TestBuilder {
         eventList.add(createPrivateGroupEvent(groupId));
         eventList.add(updateGroupTitleEvent(groupId));
         eventList.add(updateGroupDescriptionEvent(groupId));
-        eventList.add(new UpdateUserLimitEvent(groupId, "fgsadggas", Long.MAX_VALUE));
+        eventList.add(new SetLimitEvent(groupId, "fgsadggas", Long.MAX_VALUE));
         eventList.addAll(addUserEvents(membercount, groupId));
 
         return eventList;
@@ -207,7 +206,7 @@ public class TestBuilder {
         String firstname = firstname();
         String lastname = lastname();
 
-        return new AddUserEvent(
+        return new AddMemberEvent(
                 groupId,
                 userId,
                 firstname,
@@ -224,13 +223,13 @@ public class TestBuilder {
     public static List<Event> deleteUserEvents(int count, List<Event> eventList) {
         List<Event> removeEvents = new ArrayList<>();
         List<Event> shuffle = eventList.parallelStream()
-                                       .filter(event -> event instanceof AddUserEvent)
+                                       .filter(event -> event instanceof AddMemberEvent)
                                        .collect(Collectors.toList());
 
         Collections.shuffle(shuffle);
 
         for (Event event : shuffle) {
-            removeEvents.add(new DeleteUserEvent(event.getGroupid(), event.getUserid()));
+            removeEvents.add(new KickMemberEvent(event.getGroupid(), event.getTarget()));
 
             if (removeEvents.size() >= count) {
                 break;
@@ -248,13 +247,13 @@ public class TestBuilder {
      * @return Eventliste
      */
     public static List<Event> deleteUserEvents(Group group) {
-        return group.getMembers().parallelStream()
+        return group.getMemberships().parallelStream()
                     .map(user -> deleteUserEvent(group.getGroupid(), user.getUserId()))
                     .collect(Collectors.toList());
     }
 
     public static Event deleteUserEvent(UUID groupId, String userId) {
-        return new DeleteUserEvent(
+        return new KickMemberEvent(
                 groupId,
                 userId
         );
@@ -265,7 +264,7 @@ public class TestBuilder {
     }
 
     public static Event updateGroupDescriptionEvent(UUID groupId, String description) {
-        return new UpdateGroupDescriptionEvent(
+        return new SetDescriptionEvent(
                 groupId,
                 faker.random().hex(),
                 description
@@ -277,7 +276,7 @@ public class TestBuilder {
     }
 
     public static Event updateGroupTitleEvent(UUID groupId, String title) {
-        return new UpdateGroupTitleEvent(
+        return new SetTitleEvent(
                 groupId,
                 faker.random().hex(),
                 title
@@ -285,7 +284,7 @@ public class TestBuilder {
     }
 
     public static Event updateUserLimitMaxEvent(UUID groupId) {
-        return new UpdateUserLimitEvent(groupId, firstname(), Long.MAX_VALUE);
+        return new SetLimitEvent(groupId, firstname(), Long.MAX_VALUE);
     }
 
     public static Event updateRoleEvent(UUID groupId, String userId, Role role) {
@@ -297,7 +296,7 @@ public class TestBuilder {
     }
 
     public static Event deleteGroupEvent(UUID groupId) {
-        return new DeleteGroupEvent(groupId, faker.random().hex());
+        return new DestroyGroupEvent(groupId, faker.random().hex());
     }
 
     private static String firstname() {
diff --git a/src/test/java/mops/gruppen2/domain/event/AddUserEventTest.java b/src/test/java/mops/gruppen2/domain/event/AddMemberEventTest.java
similarity index 72%
rename from src/test/java/mops/gruppen2/domain/event/AddUserEventTest.java
rename to src/test/java/mops/gruppen2/domain/event/AddMemberEventTest.java
index 1f14b1c..a432517 100644
--- a/src/test/java/mops/gruppen2/domain/event/AddUserEventTest.java
+++ b/src/test/java/mops/gruppen2/domain/event/AddMemberEventTest.java
@@ -2,7 +2,7 @@ package mops.gruppen2.domain.event;
 
 import mops.gruppen2.domain.exception.GroupFullException;
 import mops.gruppen2.domain.exception.UserAlreadyExistsException;
-import mops.gruppen2.domain.model.Group;
+import mops.gruppen2.domain.model.group.Group;
 import org.junit.jupiter.api.Test;
 
 import static mops.gruppen2.TestBuilder.addUserEvent;
@@ -10,23 +10,22 @@ import static mops.gruppen2.TestBuilder.apply;
 import static mops.gruppen2.TestBuilder.createPublicGroupEvent;
 import static mops.gruppen2.TestBuilder.updateUserLimitMaxEvent;
 import static mops.gruppen2.TestBuilder.uuidMock;
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
-class AddUserEventTest {
+class AddMemberEventTest {
 
     @Test
     void applyEvent() {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
         Event updateLimitEvent = updateUserLimitMaxEvent(uuidMock(0));
-        Event addEvent = new AddUserEvent(uuidMock(0), "A", "Thomas", "Tom", "tho@mail.de");
+        Event addEvent = new AddMemberEvent(uuidMock(0), "A", "Thomas", "Tom", "tho@mail.de");
 
         Group group = apply(createEvent, updateLimitEvent, addEvent);
 
-        assertThat(group.getMembers()).hasSize(1);
-        assertThat(group.getMembers().get(0).getGivenname()).isEqualTo("Thomas");
-        assertThat(group.getMembers().get(0).getFamilyname()).isEqualTo("Tom");
-        assertThat(group.getMembers().get(0).getEmail()).isEqualTo("tho@mail.de");
+        assertThat(group.getMemberships()).hasSize(1);
+        assertThat(group.getMemberships().get(0).getGivenname()).isEqualTo("Thomas");
+        assertThat(group.getMemberships().get(0).getFamilyname()).isEqualTo("Tom");
+        assertThat(group.getMemberships().get(0).getEmail()).isEqualTo("tho@mail.de");
     }
 
     @Test
@@ -41,13 +40,13 @@ class AddUserEventTest {
 
         assertThrows(UserAlreadyExistsException.class, () -> addEventA.apply(group));
         assertThrows(UserAlreadyExistsException.class, () -> addEventC.apply(group));
-        assertThat(group.getMembers()).hasSize(2);
+        assertThat(group.getMemberships()).hasSize(2);
     }
 
     @Test
     void applyEvent_groupFull() {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
-        Event maxSizeEvent = new UpdateUserLimitEvent(uuidMock(0), "A", 2L);
+        Event maxSizeEvent = new SetLimitEvent(uuidMock(0), "A", 2L);
         Event addEventA = addUserEvent(uuidMock(0), "A");
         Event addEventB = addUserEvent(uuidMock(0), "B");
         Event addEventC = addUserEvent(uuidMock(0), "C");
@@ -55,6 +54,6 @@ class AddUserEventTest {
         Group group = apply(createEvent, maxSizeEvent, addEventA, addEventB);
 
         assertThrows(GroupFullException.class, () -> addEventC.apply(group));
-        assertThat(group.getMembers()).hasSize(2);
+        assertThat(group.getMemberships()).hasSize(2);
     }
 }
diff --git a/src/test/java/mops/gruppen2/domain/event/CreateGroupEventTest.java b/src/test/java/mops/gruppen2/domain/event/CreateGroupEventTest.java
index 93e4fdf..268b5a7 100644
--- a/src/test/java/mops/gruppen2/domain/event/CreateGroupEventTest.java
+++ b/src/test/java/mops/gruppen2/domain/event/CreateGroupEventTest.java
@@ -1,8 +1,8 @@
 package mops.gruppen2.domain.event;
 
 import mops.gruppen2.TestBuilder;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Type;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Type;
 import org.junit.jupiter.api.Test;
 
 import static mops.gruppen2.TestBuilder.uuidMock;
@@ -19,7 +19,7 @@ class CreateGroupEventTest {
 
         Group group = TestBuilder.apply(createEvent);
 
-        assertThat(group.getMembers()).hasSize(0);
+        assertThat(group.getMemberships()).hasSize(0);
         assertThat(group.getType()).isEqualTo(Type.PUBLIC);
         assertThat(group.getGroupid()).isEqualTo(uuidMock(0));
         assertThat(group.getParent()).isEqualTo(uuidMock(1));
diff --git a/src/test/java/mops/gruppen2/domain/event/DeleteGroupEventTest.java b/src/test/java/mops/gruppen2/domain/event/DestroyGroupEventTest.java
similarity index 76%
rename from src/test/java/mops/gruppen2/domain/event/DeleteGroupEventTest.java
rename to src/test/java/mops/gruppen2/domain/event/DestroyGroupEventTest.java
index db3d022..dc986ac 100644
--- a/src/test/java/mops/gruppen2/domain/event/DeleteGroupEventTest.java
+++ b/src/test/java/mops/gruppen2/domain/event/DestroyGroupEventTest.java
@@ -1,14 +1,14 @@
 package mops.gruppen2.domain.event;
 
 import mops.gruppen2.TestBuilder;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Type;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Type;
 import org.junit.jupiter.api.Test;
 
 import static mops.gruppen2.TestBuilder.uuidMock;
 import static org.assertj.core.api.Assertions.assertThat;
 
-class DeleteGroupEventTest {
+class DestroyGroupEventTest {
 
     @Test
     void applyEvent() {
@@ -16,11 +16,11 @@ class DeleteGroupEventTest {
                                                  "A",
                                                  uuidMock(1),
                                                  Type.PUBLIC);
-        Event deleteEvent = new DeleteGroupEvent(uuidMock(0), "A");
+        Event deleteEvent = new DestroyGroupEvent(uuidMock(0), "A");
 
         Group group = TestBuilder.apply(createEvent, deleteEvent);
 
-        assertThat(group.getMembers()).isEmpty();
+        assertThat(group.getMemberships()).isEmpty();
         assertThat(group.getType()).isEqualTo(null);
         assertThat(group.getLimit()).isEqualTo(0);
         assertThat(group.getGroupid()).isEqualTo(uuidMock(0));
diff --git a/src/test/java/mops/gruppen2/domain/event/EventTest.java b/src/test/java/mops/gruppen2/domain/event/EventTest.java
index f84d5a1..126fcd4 100644
--- a/src/test/java/mops/gruppen2/domain/event/EventTest.java
+++ b/src/test/java/mops/gruppen2/domain/event/EventTest.java
@@ -1,8 +1,8 @@
 package mops.gruppen2.domain.event;
 
 import mops.gruppen2.TestBuilder;
-import mops.gruppen2.domain.exception.GroupIdMismatchException;
-import mops.gruppen2.domain.model.Group;
+import mops.gruppen2.domain.exception.IdMismatchException;
+import mops.gruppen2.domain.model.group.Group;
 import org.junit.jupiter.api.Test;
 
 import static mops.gruppen2.TestBuilder.createPublicGroupEvent;
@@ -18,7 +18,7 @@ class EventTest {
 
         Group group = TestBuilder.apply(createEvent);
 
-        assertThrows(GroupIdMismatchException.class, () -> addEvent.apply(group));
+        assertThrows(IdMismatchException.class, () -> addEvent.apply(group));
     }
 
 }
diff --git a/src/test/java/mops/gruppen2/domain/event/DeleteUserEventTest.java b/src/test/java/mops/gruppen2/domain/event/KickMemberEventTest.java
similarity index 77%
rename from src/test/java/mops/gruppen2/domain/event/DeleteUserEventTest.java
rename to src/test/java/mops/gruppen2/domain/event/KickMemberEventTest.java
index fab546c..b9c9d6f 100644
--- a/src/test/java/mops/gruppen2/domain/event/DeleteUserEventTest.java
+++ b/src/test/java/mops/gruppen2/domain/event/KickMemberEventTest.java
@@ -2,28 +2,27 @@ package mops.gruppen2.domain.event;
 
 import mops.gruppen2.TestBuilder;
 import mops.gruppen2.domain.exception.UserNotFoundException;
-import mops.gruppen2.domain.model.Group;
+import mops.gruppen2.domain.model.group.Group;
 import org.junit.jupiter.api.Test;
 
 import static mops.gruppen2.TestBuilder.addUserEvent;
 import static mops.gruppen2.TestBuilder.createPublicGroupEvent;
 import static mops.gruppen2.TestBuilder.updateUserLimitMaxEvent;
 import static mops.gruppen2.TestBuilder.uuidMock;
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
-class DeleteUserEventTest {
+class KickMemberEventTest {
 
     @Test
     void applyEvent() {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
         Event updateLimitEvent = updateUserLimitMaxEvent(uuidMock(0));
         Event addEvent = addUserEvent(uuidMock(0), "A");
-        Event deleteEvent = new DeleteUserEvent(uuidMock(0), "A");
+        Event deleteEvent = new KickMemberEvent(uuidMock(0), "A");
 
         Group group = TestBuilder.apply(createEvent, updateLimitEvent, addEvent, deleteEvent);
 
-        assertThat(group.getMembers()).hasSize(0);
+        assertThat(group.getMemberships()).hasSize(0);
     }
 
     @Test
@@ -31,11 +30,11 @@ class DeleteUserEventTest {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
         Event updateLimitEvent = updateUserLimitMaxEvent(uuidMock(0));
         Event addEvent = addUserEvent(uuidMock(0), "A");
-        Event deleteEvent = new DeleteUserEvent(uuidMock(0), "B");
+        Event deleteEvent = new KickMemberEvent(uuidMock(0), "B");
 
         Group group = TestBuilder.apply(createEvent, updateLimitEvent, addEvent);
 
         assertThrows(UserNotFoundException.class, () -> deleteEvent.apply(group));
-        assertThat(group.getMembers()).hasSize(1);
+        assertThat(group.getMemberships()).hasSize(1);
     }
 }
diff --git a/src/test/java/mops/gruppen2/domain/event/UpdateGroupDescriptionEventTest.java b/src/test/java/mops/gruppen2/domain/event/SetDescriptionEventTest.java
similarity index 60%
rename from src/test/java/mops/gruppen2/domain/event/UpdateGroupDescriptionEventTest.java
rename to src/test/java/mops/gruppen2/domain/event/SetDescriptionEventTest.java
index ea61295..e607368 100644
--- a/src/test/java/mops/gruppen2/domain/event/UpdateGroupDescriptionEventTest.java
+++ b/src/test/java/mops/gruppen2/domain/event/SetDescriptionEventTest.java
@@ -1,21 +1,20 @@
 package mops.gruppen2.domain.event;
 
 import mops.gruppen2.TestBuilder;
-import mops.gruppen2.domain.exception.BadParameterException;
-import mops.gruppen2.domain.model.Group;
+import mops.gruppen2.domain.exception.BadArgumentException;
+import mops.gruppen2.domain.model.group.Group;
 import org.junit.jupiter.api.Test;
 
 import static mops.gruppen2.TestBuilder.createPublicGroupEvent;
 import static mops.gruppen2.TestBuilder.uuidMock;
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
-class UpdateGroupDescriptionEventTest {
+class SetDescriptionEventTest {
 
     @Test
     void applyEvent() {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
-        Event updateEvent = new UpdateGroupDescriptionEvent(uuidMock(0), "A", "desc.");
+        Event updateEvent = new SetDescriptionEvent(uuidMock(0), "A", "desc.");
 
         Group group = TestBuilder.apply(createEvent, updateEvent);
 
@@ -25,10 +24,10 @@ class UpdateGroupDescriptionEventTest {
     @Test
     void applyEvent_badDescription() {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
-        Event updateEventA = new UpdateGroupDescriptionEvent(uuidMock(0), "A", "");
+        Event updateEventA = new SetDescriptionEvent(uuidMock(0), "A", "");
 
         Group group = TestBuilder.apply(createEvent);
 
-        assertThrows(BadParameterException.class, () -> updateEventA.apply(group));
+        assertThrows(BadArgumentException.class, () -> updateEventA.apply(group));
     }
 }
diff --git a/src/test/java/mops/gruppen2/domain/event/UpdateUserLimitEventTest.java b/src/test/java/mops/gruppen2/domain/event/SetLimitEventTest.java
similarity index 62%
rename from src/test/java/mops/gruppen2/domain/event/UpdateUserLimitEventTest.java
rename to src/test/java/mops/gruppen2/domain/event/SetLimitEventTest.java
index f28ffa9..d4e148c 100644
--- a/src/test/java/mops/gruppen2/domain/event/UpdateUserLimitEventTest.java
+++ b/src/test/java/mops/gruppen2/domain/event/SetLimitEventTest.java
@@ -1,22 +1,21 @@
 package mops.gruppen2.domain.event;
 
-import mops.gruppen2.domain.exception.BadParameterException;
-import mops.gruppen2.domain.model.Group;
+import mops.gruppen2.domain.exception.BadArgumentException;
+import mops.gruppen2.domain.model.group.Group;
 import org.junit.jupiter.api.Test;
 
 import static mops.gruppen2.TestBuilder.addUserEvent;
 import static mops.gruppen2.TestBuilder.apply;
 import static mops.gruppen2.TestBuilder.createPublicGroupEvent;
 import static mops.gruppen2.TestBuilder.uuidMock;
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
-class UpdateUserLimitEventTest {
+class SetLimitEventTest {
 
     @Test
     void applyEvent() {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
-        Event updateEvent = new UpdateUserLimitEvent(uuidMock(0), "A", 5L);
+        Event updateEvent = new SetLimitEvent(uuidMock(0), "A", 5L);
 
         Group group = apply(createEvent, updateEvent);
 
@@ -26,24 +25,24 @@ class UpdateUserLimitEventTest {
     @Test
     void applyEvent_badParameter_negative() {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
-        Event updateEvent = new UpdateUserLimitEvent(uuidMock(0), "A", -5L);
+        Event updateEvent = new SetLimitEvent(uuidMock(0), "A", -5L);
 
         Group group = apply(createEvent);
 
-        assertThrows(BadParameterException.class, () -> updateEvent.apply(group));
+        assertThrows(BadArgumentException.class, () -> updateEvent.apply(group));
     }
 
     @Test
     void applyEvent_badParameter_tooSmall() {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
-        Event updateEventA = new UpdateUserLimitEvent(uuidMock(0), "A", 5L);
+        Event updateEventA = new SetLimitEvent(uuidMock(0), "A", 5L);
         Event addEventA = addUserEvent(uuidMock(0));
         Event addEventB = addUserEvent(uuidMock(0));
         Event addEventC = addUserEvent(uuidMock(0));
-        Event updateEventB = new UpdateUserLimitEvent(uuidMock(0), "A", 2L);
+        Event updateEventB = new SetLimitEvent(uuidMock(0), "A", 2L);
 
         Group group = apply(createEvent, updateEventA, addEventA, addEventB, addEventC);
 
-        assertThrows(BadParameterException.class, () -> updateEventB.apply(group));
+        assertThrows(BadArgumentException.class, () -> updateEventB.apply(group));
     }
 }
diff --git a/src/test/java/mops/gruppen2/domain/event/UpdateGroupTitleEventTest.java b/src/test/java/mops/gruppen2/domain/event/SetTitleEventTest.java
similarity index 61%
rename from src/test/java/mops/gruppen2/domain/event/UpdateGroupTitleEventTest.java
rename to src/test/java/mops/gruppen2/domain/event/SetTitleEventTest.java
index 497d5e7..04cfd4f 100644
--- a/src/test/java/mops/gruppen2/domain/event/UpdateGroupTitleEventTest.java
+++ b/src/test/java/mops/gruppen2/domain/event/SetTitleEventTest.java
@@ -1,21 +1,20 @@
 package mops.gruppen2.domain.event;
 
 import mops.gruppen2.TestBuilder;
-import mops.gruppen2.domain.exception.BadParameterException;
-import mops.gruppen2.domain.model.Group;
+import mops.gruppen2.domain.exception.BadArgumentException;
+import mops.gruppen2.domain.model.group.Group;
 import org.junit.jupiter.api.Test;
 
 import static mops.gruppen2.TestBuilder.createPublicGroupEvent;
 import static mops.gruppen2.TestBuilder.uuidMock;
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
-class UpdateGroupTitleEventTest {
+class SetTitleEventTest {
 
     @Test
     void applyEvent() {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
-        Event updateEvent = new UpdateGroupTitleEvent(uuidMock(0), "A", "title.");
+        Event updateEvent = new SetTitleEvent(uuidMock(0), "A", "title.");
 
         Group group = TestBuilder.apply(createEvent, updateEvent);
 
@@ -25,10 +24,10 @@ class UpdateGroupTitleEventTest {
     @Test
     void applyEvent_badDescription() {
         Event createEvent = createPublicGroupEvent(uuidMock(0));
-        Event updateEventA = new UpdateGroupTitleEvent(uuidMock(0), "A", "");
+        Event updateEventA = new SetTitleEvent(uuidMock(0), "A", "");
 
         Group group = TestBuilder.apply(createEvent);
 
-        assertThrows(BadParameterException.class, () -> updateEventA.apply(group));
+        assertThrows(BadArgumentException.class, () -> updateEventA.apply(group));
     }
 }
diff --git a/src/test/java/mops/gruppen2/domain/event/UpdateRoleEventTest.java b/src/test/java/mops/gruppen2/domain/event/UpdateRoleEventTest.java
index fee6206..257e6e4 100644
--- a/src/test/java/mops/gruppen2/domain/event/UpdateRoleEventTest.java
+++ b/src/test/java/mops/gruppen2/domain/event/UpdateRoleEventTest.java
@@ -1,8 +1,8 @@
 package mops.gruppen2.domain.event;
 
 import mops.gruppen2.domain.exception.UserNotFoundException;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Role;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Role;
 import org.junit.jupiter.api.Test;
 
 import static mops.gruppen2.TestBuilder.addUserEvent;
@@ -10,7 +10,6 @@ import static mops.gruppen2.TestBuilder.apply;
 import static mops.gruppen2.TestBuilder.createPublicGroupEvent;
 import static mops.gruppen2.TestBuilder.updateUserLimitMaxEvent;
 import static mops.gruppen2.TestBuilder.uuidMock;
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
 class UpdateRoleEventTest {
diff --git a/src/test/java/mops/gruppen2/domain/service/EventStoreServiceTest.java b/src/test/java/mops/gruppen2/domain/service/EventStoreServiceTest.java
index 5b00a69..b125752 100644
--- a/src/test/java/mops/gruppen2/domain/service/EventStoreServiceTest.java
+++ b/src/test/java/mops/gruppen2/domain/service/EventStoreServiceTest.java
@@ -2,7 +2,7 @@ package mops.gruppen2.domain.service;
 
 import mops.gruppen2.Gruppen2Application;
 import mops.gruppen2.domain.event.Event;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.model.group.User;
 import mops.gruppen2.persistance.EventRepository;
 import mops.gruppen2.persistance.dto.EventDTO;
 import org.junit.jupiter.api.BeforeEach;
@@ -73,7 +73,7 @@ class EventStoreServiceTest {
         EventDTO dto = EventStoreService.getDTOFromEvent(event);
 
         assertThat(dto.getGroup_id()).isEqualTo(event.getGroupid().toString());
-        assertThat(dto.getUser_id()).isEqualTo(event.getUserid());
+        assertThat(dto.getUser_id()).isEqualTo(event.getTarget());
         assertThat(dto.getEvent_id()).isEqualTo(null);
         assertThat(dto.getEvent_type()).isEqualTo("CreateGroupEvent");
     }
diff --git a/src/test/java/mops/gruppen2/domain/service/GroupServiceTest.java b/src/test/java/mops/gruppen2/domain/service/GroupServiceTest.java
index ac09bc0..8f1c94a 100644
--- a/src/test/java/mops/gruppen2/domain/service/GroupServiceTest.java
+++ b/src/test/java/mops/gruppen2/domain/service/GroupServiceTest.java
@@ -3,9 +3,9 @@ package mops.gruppen2.domain.service;
 import mops.gruppen2.Gruppen2Application;
 import mops.gruppen2.TestBuilder;
 import mops.gruppen2.domain.event.Event;
-import mops.gruppen2.domain.model.Group;
-import mops.gruppen2.domain.model.Type;
-import mops.gruppen2.domain.model.User;
+import mops.gruppen2.domain.model.group.Group;
+import mops.gruppen2.domain.model.group.Type;
+import mops.gruppen2.domain.model.group.User;
 import mops.gruppen2.persistance.EventRepository;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Disabled;
@@ -82,7 +82,7 @@ class GroupServiceTest {
         List<Group> groups = ProjectionService.projectGroups(eventList);
 
         assertThat(groups).hasSize(1);
-        assertThat(groups.get(0).getMembers()).hasSize(5);
+        assertThat(groups.get(0).getMemberships()).hasSize(5);
         assertThat(groups.get(0).getType()).isEqualTo(Type.PRIVATE);
     }
 
@@ -95,7 +95,7 @@ class GroupServiceTest {
         List<Group> groups = ProjectionService.projectGroups(eventList);
 
         assertThat(groups).hasSize(20);
-        assertThat(groups.stream().map(group -> group.getMembers().size()).reduce(Integer::sum).get()).isEqualTo(70);
+        assertThat(groups.stream().map(group -> group.getMemberships().size()).reduce(Integer::sum).get()).isEqualTo(70);
     }
 
     //TODO: EventStoreServiceTest