How to play music on my kyrocera event?

I have this garbage kyrocera phone from before I got my iPhone. I want to use it as a music player but it keeps telling me it can't play the song for nearly 3/4 of my music. Is there an app I can install or something I can do because most of the music are songs I enjoy listening to.

I know it's something with the phone because the files play from my computer and I'm pretty sure it's fixable because I fixed it when I was using the phone but I've forgotten since I got an iPhone.

I'd like to know sooner rather than later because I want to have music for work.

Use your iPhone for music & get on with your life.