Move Navigation Bar

Me again, sorry for bothering you so much. ^^ I would like to move the navigation bar under the header image. I used margin-top for that, but something strange happened: now when the WP Editor shows the page like I wanted - with the navigation bar directly underneath the image - it's displaced when I check the website and hides a part of the header image. I changed it so that there is some space in the editor, but it appears that the navigation bar is changing it's position on different screens. So when I thought it was alright on another screen the navigation bar was displaced again. Do I have to change something else, to make it work? website: talkingstories.de