Forza and Party Xbox is not working?

For half a year I have an Xbox One S, since the beginning I could not go to parties and not play Forza Horizon 3 and 4 online. We have a 60k line from 1&1 and a home server from Fritz Box. Please help me (all ports released did not work)

Thanks to all the good answers 😇

Please write a rationale have accidentally taken a survey 😬

Look if your NAT is open. If it is closed, it will happen to you even more. Was with me too.