Thank you for your answer. There were no additional settings for the image. But I found out that within the Box-Model there must be set 32px for top-margin somewhere. I couldn’t find it but it helped to set an additional css rule under wrapper page Backround under General Appereance: {margin-top: -36px !Important}.
Regarding your remark on the full conversion to Xtreme: yes I know that, but I didn’t dare so far…. never change a running system….