[Theme: German Newspaper] Header problem…………just doesnt show up

Hi, I have the german newspaper theme, I am trying to change the header, I’ve uploaded the image to my library and pasted the url in the header image opetion, but the image does not show on the website; did other people encounter this; does the image have to be an exact pixel ratio and size; what am i doint wrong……..

https://www.ads-software.com/extend/themes/german-newspaper/