Thanks for your reply ... out of the wall comes a RJ11 .. and the fritzbox has a RJ45.
In the past i also had a 7170 .. that came with a Y-split cable. With on one site a RJ45 and on the other site 2x RJ11
my 7170 came with this box:
so .. RJ11 from wall to this box .. Y-split cable had 2x...