How to remove the black space above the header?

Hi, I have just installed your theme, and I love it! I have one problem, when I view my site on a mobile I can see a black space above the header?! The header doesn’t fill the whole screen as in your mobile demo. So, how do I get rid of that? I thank you in advance!

My website is


It is because of a plugin for login, link is not showing on mobile but space remains.

Best Regards