Background not saved

Hello, when i try to set an image as background i can select an image from the media and adjust it to the screen size. When i save the settings and re3call the website from the browser to check the installation the picture is not visible (blanc). And no - its not hidden behind the content side - its apparently just not saved. I tried this with various pictures and various sizes. Catchbase pro, www.stichel-online.de, Could you pls check on this subject and get back to me. Thank you very much Mind regards, Michael