Menu not working on telephone

I need help with my wordpress theme GreatMag.
I am helping out making this website https://www.lemonit.nl and everything was working fine.
By checking on a phone the hamburger menu was not working.

I created another site with the same theme to check out and there the menu is working.

I tried to reinstall the theme but still not working.

I need help. Can anyone help me out? I checked with the analyser but can’t seem to get what is wrong with it. Nothing is deleted, only designed in other colors.