Problem solved, thanks guys !!!
There was one cable cut - unbelieveable. It was the wire to pin 1 (ground) that was broken on the GM3 module plug on interface X332. There was no error code visible.
Symptoms (there were strange ones):
remote locking/unlocking via key doesn't work
mechanical locking of the driver door doesn't lock the other doors
lower tailgate doesn't open any more
upper tailgate cannot be locked in any way
front wipers not working
power steering not as strong as it should be !!!
fixing that cable fixed all these issues.
Learnings: if you ever connect something to your wires and see such a thing as in the picture. Take it and throw it away as far as you can.
Regards, H