Music library won't sync to iphone, how do I clean up my phone?

My iphone music is a mess and won't sync with itunes.

I have tried -

Downloading all manually that could from the cloud.

Downloading all purchases manually.

Turning of show all music. *with a power off

Manually deleting all songs.

Nothing works and itunes will not sync.

Most of the songs are greyed out when I show my iphone in itunes.

How do I wipe out all the music on my phone and start a fresh sync? Or second question, do I just need to do a restore?

I have been struggling with this since December and am ready to scream!