Rock star pro Theme

Hello, I already worked on this theme and I really like it but when I scroll down on my iPhone and iPad the background stays on the bottom .On the editing site it is ok on the view tablet and phone but it is not when i try them on my other devices . For example the background is a picture and when I scroll down it stays in the middle and the letters moving up and down .On my computer it is fine when i use it on my iPhone the photo is on the bottom and when I scroll down and up it is only a black background . How to fix this? Zoltan Nagy zoltan.lucaz@yahoo.com Lucaz Film Thank You