Resolved Dark Line unter Header - Helix Ultimate Template

Hello,

the website i am working on (http://www.physio-nienhagen.de) shows a dark line underneath the header menu (see DarkLine.png). I have checked all background colors and they don't make this problem. Do you have an idea what could make this issue?

I found the following in the internet:

#sp-header {

position: absolute;

}

I placed this in the custom css of the template and the dark line disapperaes.

But the top part of the big image is missing then on mobile devices (see Mobile.jpg)
On Desktop Computers the Logo is misplaced over the big image (see Desktop.png)

Activated Template is shaper_helixultimate - Default

Any ideas?

Kind regards
Benjamin