I tried to deactivating installed plugins but with no effect unfortunately.
I still have 2 plugins active but I manage another website with the Ample theme (www.eddymoust.nl) and the same plugins are working fine for this website –> responsive menu is showing on ipad and iphone.
Is there something else I can try for www.demianpolane.nl ?
We’re not sure where it comes from. But we can see it and it is the reason for your issue.
The code might be generated by the plugin you’re using or maybe you’ve been added since this has not come from our theme.