i don’t have the link atm, but there’s a list of recommended therapists out there somewhere by a german trans org. mine gave me the letter after one meeting
the endo will probably ask about freezing sperm, if that’s something you wanna do getting it out of the way before then might speed things up (mine wouldn’t let me on until that was done because it’ll complicate shit)
as for a time frame, from making the first appointment to getting the first prescription was about a year for me, most of it waiting for appointments
sadly, making appointments, waiting, and hoping for the best is about all you can do as far as i‘m aware. maybe changing your name and gender marker via selbstbestimmungsgesetz will help speed things up, if that happens before any major appointments can be made