Space below header

So, I tried googling around and scrolling through posts here so far no luck.
On the my site test.schoolgrappling.be there is a space between the header (top menu) and the start of the body of the page. When trying to “inspect”that part of the page, impossible to nail it down, it doesn’t seem to exist.
I would like to header to look like the top of the page at bbjja.be (from which I used the page template).

Thanks for your help!

The page I need help with: [log in to see the link]