Erasing all songs from iPhone

Howdy, I'm trying to delete all the music on my iPhone. On the App on my iPhone there is nothing to see ... no song, no artist, no nothing.

But when I plug in my iPhone to my iMac and open the Music-App - BOOM!!! A big music list appears.

So I select them all and trying to delete those songs ... nothing happens and the list ist still there.

Even when I got on my Settings / General / iPhone Storage information ... Music App is 23,8 MB and Dokuments & Data at 102,8 MB ( <- where can I get these information or just see what's in there??? )

please help !!!

Marc