So…
I tried my Xbox controller in FS2020 and it worked perfectly.
But somehow after randomly trying some keyboard commands the increase throttle (A) and decrease throttle (B) only workes while pressing CTRL at the same time and even then it goes strains to max/min (hopeless).
I tried restarting the game + reseting default setting. But still the same issue.
Any chance someone knows who to fix this problem?