Can still not connect iPhone 11 on iOS 14.1 to iTunes x64 (non-Windows Store version)

For general advice see Troubleshooting issues with iTunes for Windows updates.

The steps in the second box are a guide to removing everything related to iTunes and then rebuilding it which is often a good starting point unless the symptoms indicate a more specific approach. When reinstalling right click on the downloaded setup file and use run as administrator. It may also help to temporarily disable any non-Microsoft anti-virus.

Review the other boxes and the list of support documents further down the page in case one of them applies.

The further information area has direct links to the current and recent builds in case you have problems downloading, or want to revert to an older version if the current one won't work properly for you at the moment. Links to the most recent builds are now at the bottom of the page.

Your library and device backups should be unaffected by these steps but there are links to backup and recovery advice should it be needed.

tt2

See Recover media from an iPod - Apple Community. While iTunes may have decided that the device needs a reset and cannot be convinced otherwise perhaps you can use one of the third party tools to extract your media. You could then try backing up the device to iCloud, restore it, and then add media back from iTunes.

You can also try Apple Support but I don't know how likely you are to get through to anyone able to help you gather and diagnose log files or provide a targeted fix for the problem you're currently seeing. In general nuke and pave is the way to go, but you need a suitable backup and your media collection stored safely somewhere for that to be a viable approach.

tt2

The year of German I did over 40 years ago isn't enough for me to read that message but I'm guessing it is similar to the warning I've described here:

If Windows warns about compatibility testing or similar tell it continue anyway.

It should be possible to tell Windows to use your selected .inf file, and that should resolve the issue.

tt2

Can you please post a screenshot of the warning at step 10? You should be able to tell Windows to proceed to use the selected file even if it has reservations.

tt2