How to troubleshoot a failing starter in an Audi 80?

I have recently been experiencing issues with my Audi 80's starter, causing it to fail to start. I have tried jump starting the car, but it still does not work. What could be the possible reasons for this and how can it be fixed?

One possible reason for a failing starter in an Audi 80 could be a faulty solenoid. This is a small electrical component that is responsible for connecting the starter to the battery. If this is the case, it is recommended to replace the solenoid.