Hi, ** hast die Antwort schon in der deutschen Community auf deine gleiche Frage erhalten. Speziell für dich übersetzt:
Riccardo, Christine is right. Playlists do not store tracks. The media library consists of albums where tracks are stored, and playlists use the tracks by referring to the tracks in the album.
This way, you can have the same track in multiple playlists without needing additional storage in the media library.
Therefore, you must not delete the entire album if you want to keep individual tracks from it.
To achieve what you want, delete only the tracks you never want to hear again from the media library directly from the album (using ... < Delete from Media Library), but spare the tracks you want to keep. This is the only way they can continue to be used in playlists.
Enjoy
Reiner