Speedometer Malfunction: Electronics Problem

Hey everyone, the speedometer in my Passat is acting up.
Sometimes it works perfectly normally, sometimes it doesn't work at all, and then it starts behaving like a tachometer.
What could that be? Is there anything I can do about it myself?

Greetings, papatom.

Hello,

You can find the engine code on the first page of the service booklet.
Before you start replacing any sensors (e.g., speed sensor), you should have the instrument cluster's error memory read.