Hello Guido,
Without a wiring diagram, you will hardly get very far:
https://erwin.skoda-auto.cz
I would focus on checking for cold solder joints, defective electrolytic capacitors, and the power supply to the AI chip. If nothing obvious is apparent there:
Without much time or expertise, visiting a Skoda workshop will be the quickest solution in this case. Ask there if a used instrument cluster (WFS) can be adapted, which would be cheaper than a new one.
Best regards, Rainer.