Switch off Hamburger-Menu

Hello, everyone.
I have changed the navigation of my site so that I don’t want a hamburger menu in the mobile view anymore. How can I switch this off, because now I get a white, empty area in the landscape view - but only in the landscape view. See attached screenshot.
Thank you very much!

Excuse me, folks,
I’m an idiot… my picture is too small in landscape view on the iPhone.
On the iPad, however, it is scaled correctly.

Sorry, can I delete the thread?