Can't download songs for offline mode

[ianpls]

I am using a Samsung Galaxy A8 and recently, all 1004 of my offline songs have been deleted. I've tried reinstalling the app and clearing storage data but it only made it worse to where when I'm downloading the songs and i hit the stop download button, all the previously downloaded songs would be wiped out as well. Usually doing so would only pause the download and the downloaded songs would remain. Also, the 1004 songs would take up around 2.5Gb or slightly more, however, it says that i have 650Mb used up in my storage, even when all my offline songs are deleted. This is really frustrating and i do not know how to fix this. Please help me.