My songs are being deleted from local files as I add them to a playlist

[Omarproductions]

Hi, I'm new to Spotify so bare with me. So I'm trying to add songs that I've made to my own playlist and not make it public; However, after I do this, the songs disappear from spotify desktop and the playlist can't be played in spotify mobile. I can tell because when I try to play the playlist on my phone, no songs appear, and on the desktop when I go to local files, the songs disappear. It did work one time, but soon afterwards my songs got deleted. I don't know if it's because my musics are mashups and contain copyrighted music, but I just want to enjoy the music I've created on the go. Any help is appreciated, thank you.