Thank you for the hint.
I gonna need a bit more help to do this.
The code I provided is from another source and I did only adjust it to my needs.
I can do that, but making up the code from zero I don't have enough knowledge.
I am a trained media designer and music producer, so the device I built is a MIDI controller for the studio. I am happy I got this far and it is working. Also have basics in electronics, so that part was easy for me.
The display programming seems not that easy to start.
If I would have the first potentiometer working, then I gonna figure out the rest.
Maybe you could help me a bit further, based on my code?