Menu on home by display of Iphone X with safari and Chrome

Hoi, I'm using theme Catch Fullscreen - pro. So far so good but when using the hamburger menu on home/first screen the top of the menu is not showing. After scrolling down one section using the hamburger menu gives no problem. I don't the same on Firefox. Can you help? Site is in construction: https://www.gocce.nl Thanks in advance Paola Palma