all my music is tagged correctly and has embedded cover
(eg.: on windows10= ok; on IOS iPad=ok)

i'm using SAMSUNG GALAXY A5 (2016) with additional 32-gb sd-card.
on this card i've placed my music-folder (without sub-folders)
Media Library: contains all tracks
Music folders: contains my music-folder on ext. sd-card
Playlist-folders: empty
foobar2000 music folder: is empty
External Storage: shows all music with covers
Playlist: shows all tracks (without cover; don't know if it should)
playing a track: no artist, no album, no title, no cover

what i'm doing wrong ?