piccobello

Thank you, I will do that!

Thanks, yes I have – but I dont quite understand how to use them – especially in my case

I have found my solution, according to this post on stackoverflow:
https://stackoverflow.com/questions/7526113/load-wordpress-post-content-into-div-using-ajax

YEAH, I found the solution for having a fullscreen image with ratio, simply put this into the custom field:

background-position: center top;
background-attachment: fixed;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;

It seems like dills solved his problem.
Could somebody point out the solution?