db={"Role":[{"RoleId":1,"Name":"Student"},{"RoleId":2,"Name":"Teacher"}],"People_Course_Grade":[{"People_Course_GradeId":1,"PeopleId":1,"CourseId":1},{"People_Course_GradeId":2,"PeopleId":2,"CourseId":1},{"People_Course_GradeId":3,"PeopleId":3,"CourseId":2},{"People_Course_GradeId":4,"PeopleId":1,"CourseId":2}],"Course":[{"CourseId":1,"Name":"Java"},{"CourseId":2,"Name":"Java II"},{"CourseId":3,"Name":"Statistik 1"}]}

db.People_Course_Grade.aggregate([{$lookup:{from:"Role",localField:"PeopleId",foreignField:"RoleId",as:"people"}},{$lookup:{from:"Course",localField:"CourseId",foreignField:"CourseId",as:"course"}},{$replaceRoot:{newRoot:{$mergeObjects:["$$ROOT",{$arrayElemAt:["$people",0]},{$arrayElemAt:["$course",0]},]}}},{$project:{people:0,course:0}}])