FIrst of all thanks for the quick reply, I will note that I am just a hobby Simmer and dont know soooo much.
Since I am done flying, and landed manually and without ILS (Because it also didnt work) I cannot tell if DOMEG was in my Flightplan.
What I can say is, that yesterday on a different route the same thing occured. My plane followed the FP but always 8NM left or in that specific case right to it.
The result is always the same, i miss the approach due the difference between my route and the A320. (i think thats why ILS is not beeping and working)
I did some research and it might be the case that the flightplan is not connected to the FBW A320 MCDU so I will watch a guide now how to set up Sim Brief and load the Flightplan onto the integrated IPad in the A320.