Rockstar Theme Mobile issues

This theme is 100% great when it comes to viewing it on a computer. However when I view it on Mobile IOS devices issues arise. -My background does not move with the page. It is stretched out super wide and pixelates. I have tried every setting in the backgrounds to fix this but nothing works there. -Also when I scroll down the Instagram pictures are distorted and large. Here is the website www.zachkleisinger.com thanks