iTunes Music Library messed up

hello

My iTunes library is a total mess! Titles, albums and artists are confused. I can choose Jimmy Hendrix and I'm playing Mozart... the problems are not only for single albums, but for the whole library.

Which I already tried to do:

iTunes: Organize a media library

iTunes: Albums deleted from the library and reloaded from Apple Music > the next time you sync, the same chaos will reappear.....

Apple Support: called and looked for solutions together (approx. 2 hours)

No improvement of the situation!

Has anyone had similar experiences and knows a solution?

Thank you (screenshot is showing Artist "The National", Albums are showing wrong cover, Tracklist from various sources. They sometimes seem to match the original Tracklist of the album, but wait until you play them....)