Back derailler bent? Novice

ScottdonoMTB

I have been mountain biking for around one year and wanted to take the technical parts my self, my back derailler the silver part what the chain goes on has bent towards the spokes and the chain just keeps slipping off?
Any ideas how to fix this, or should I buy a new derailler complete?
thanks

cooldad

The hanger or the cage?
Read Parktools.
Generally not repairable.