make a query in controller

Hello , i am trying to pass all the dissertations where exists on my DB from the specific Auth::user, connected with internal_examiner_id which is user's id. in this line 'dissertations' =>Dissertation::all()->where('internal_examiner_id','12'), I am trying to make the number 12 dynamic, i want to use the Auth::user's id, ive tried Auth::user()->id,tried to make a variable called $query = auth()->user()->id; and pass it instead of 12 and some other ways with no luck.. Any suggestions? ​```