diff --git a/backend/src/entities/assignments/group.entity.ts b/backend/src/entities/assignments/group.entity.ts
index 213e0f38..e26dcbe1 100644
--- a/backend/src/entities/assignments/group.entity.ts
+++ b/backend/src/entities/assignments/group.entity.ts
@@ -18,6 +18,8 @@ export class Group {
 
     @ManyToMany({
         entity: () => Student,
+        owner: true,
+        inversedBy: "groups"
     })
-    members!: Student[];
+    members: Collection<Student> = new Collection<Student>(this);
 }
diff --git a/backend/src/entities/classes/class.entity.ts b/backend/src/entities/classes/class.entity.ts
index 63315304..7ad66c52 100644
--- a/backend/src/entities/classes/class.entity.ts
+++ b/backend/src/entities/classes/class.entity.ts
@@ -14,9 +14,9 @@ export class Class {
     @Property({ type: 'string' })
     displayName!: string;
 
-    @ManyToMany(() => Teacher)
+    @ManyToMany({entity: () => Teacher, owner: true, inversedBy: 'classes'})
     teachers!: Collection<Teacher>;
 
-    @ManyToMany(() => Student)
+    @ManyToMany({entity: () => Student, owner: true, inversedBy: 'classes'})
     students!: Collection<Student>;
 }
diff --git a/backend/src/entities/users/student.entity.ts b/backend/src/entities/users/student.entity.ts
index 58e82765..2c4cfb68 100644
--- a/backend/src/entities/users/student.entity.ts
+++ b/backend/src/entities/users/student.entity.ts
@@ -8,9 +8,9 @@ import { StudentRepository } from '../../data/users/student-repository.js';
     repository: () => StudentRepository,
 })
 export class Student extends User {
-    @ManyToMany(() => Class)
+    @ManyToMany({entity: () => Class, mappedBy: 'students'})
     classes!: Collection<Class>;
 
-    @ManyToMany(() => Group)
-    groups!: Collection<Group>;
+    @ManyToMany({entity: () => Group, mappedBy: 'members'})
+    groups: Collection<Group> = new Collection<Group>(this);
 }
diff --git a/backend/src/entities/users/teacher.entity.ts b/backend/src/entities/users/teacher.entity.ts
index d53ca603..900e3610 100644
--- a/backend/src/entities/users/teacher.entity.ts
+++ b/backend/src/entities/users/teacher.entity.ts
@@ -5,6 +5,6 @@ import { TeacherRepository } from '../../data/users/teacher-repository.js';
 
 @Entity({ repository: () => TeacherRepository })
 export class Teacher extends User {
-    @ManyToMany(() => Class)
+    @ManyToMany({entity: () => Class, mappedBy: 'teachers'})
     classes!: Collection<Class>;
 }
diff --git a/backend/src/middleware/error-handling/error-handler.ts b/backend/src/middleware/error-handling/error-handler.ts
index d7315603..ff3add3a 100644
--- a/backend/src/middleware/error-handling/error-handler.ts
+++ b/backend/src/middleware/error-handling/error-handler.ts
@@ -9,7 +9,7 @@ export function errorHandler(err: unknown, _req: Request, res: Response, _: Next
         logger.warn(`An error occurred while handling a request: ${err} (-> HTTP ${err.status})`);
         res.status(err.status).json(err);
     } else {
-        logger.error(`Unexpected error occurred while handing a request: ${JSON.stringify(err)}`);
+        logger.error(`Unexpected error occurred while handing a request: ${err}`);
         res.status(500).json(err);
     }
 }
diff --git a/backend/src/services/groups.ts b/backend/src/services/groups.ts
index 393268c1..ec152da4 100644
--- a/backend/src/services/groups.ts
+++ b/backend/src/services/groups.ts
@@ -1,4 +1,4 @@
-import { Collection, EntityDTO } from '@mikro-orm/core';
+import { EntityDTO } from '@mikro-orm/core';
 import { getGroupRepository, getStudentRepository, getSubmissionRepository } from '../data/repositories.js';
 import { Group } from '../entities/assignments/group.entity.js';
 import { mapToGroupDTO, mapToGroupDTOId } from '../interfaces/group.js';
@@ -9,8 +9,6 @@ import { fetchAssignment } from './assignments.js';
 import { NotFoundException } from '../exceptions/not-found-exception.js';
 import { putObject } from './service-helper.js';
 import { Student } from '../entities/users/student.entity.js';
-import { GroupRepository } from '../data/assignments/group-repository.js';
-import { assert } from 'console';
 
 export async function fetchGroup(classId: string, assignmentNumber: number, groupNumber: number): Promise<Group> {
     const assignment = await fetchAssignment(classId, assignmentNumber);
@@ -72,17 +70,13 @@ export async function createGroup(groupData: GroupDTO, classid: string, assignme
     ).filter((student): student is Student => student !== null);
 
     const assignment = await fetchAssignment(classid, assignmentNumber);
-    
+
     const groupRepository = getGroupRepository();
     const newGroup = groupRepository.create({
         assignment: assignment,
-        members: members,
+        members: members
     });
 
-    assert(newGroup.groupNumber !== undefined, "NO GROUPNUMBER WAS ASSIGNED");
-
-    console.log(newGroup);
-
     try {
         await groupRepository.save(newGroup);
     } catch(e) {