Playlist and Song Removal (from Iphone 7)

[wallino]

Hi All,
I've downloaded the songs and made my playlists. Now I want to delete some songs from the playlist so i select it and clicked on "remove".

The song are not available on my "Song list" but it still be in the playlist and I cannot remove from there!.
How can I remove from there without remove the playlist?

Other things I've noticed that if I remove a song, and Save again, the song are saved in 0 seconds, like it still present. It's normal? How to permanently delete a song to save space?

Thank you so much!