Imported mp3 music is gone

Since the last weekend I did some changes in the iCloud settings about "optimizing" the storage but I cannot repeat what I did there - sorry! Anyhow, since this changes all my imported music albums are gone, went to nirvana, except one album which I bought once at the Apple Store (.. or whatever this "store" is called :).

I copied nearly all my music from bought CD's as mp3 to my music app, also to be independent from any internet connection. Since it is very annoying and frustrating to start again reinstalling the CD's I have the hope that anybody has had the same problem and hopefully solved it. I have the newest iOS (17.4) and macOS (Sonoma 14.4) installed on my devices.

Does anybody have had the same problem? Does there exist any "magic button" to restore the lost music? Can anybody give me a hint where to read more about restoring lost albums? Any help is very appreciated.

By the way, I never accepted Apple Music which may now turn out as a disadvantage.

All the best!