How to troubleshoot a failing starter in an Audi A2?

My Audi A2 is having issues starting and I suspect it may be a failing starter. I have checked the battery and it seems to be fine. Can anyone provide some insight on how to further diagnose the issue and potentially fix it?

First, I would recommend checking the connections between the battery and the starter. Sometimes loose or corroded connections can cause starting issues. If that doesn't solve the issue, you may need to replace the starter.