@stijnbiemans – I had a look at your site but I’m not clear what you mean by “the toggle button is inversed (lights up when not visible),” as the correct icons seem to be lighter when active/open. Could you describe the issue in more detail?
Please start a new thread here so the original poster doesn’t continue to get email notifications:
https://www.ads-software.com/support/theme/hexa#new-topic-0
When you do, please provide a screenshot pointing out the issue you’re trying to solve. You can upload the screenshot – in a graphic format like JPG, PNG, or GIF – in your Media Library, and provide a link so I can see it, or upload it with a service like Cloudup, Imgur or Snaggy.
Furthermore, is it possible to not show the menu by default when on mobile?
Yes, you can wrap the CSS in a media query to restrict the change to happen above a specific screen size.
https://en.support.wordpress.com/custom-design/custom-css-media-queries/
https://css-tricks.com/snippets/css/media-queries-for-standard-devices/
https://webdesignerwall.com/tutorials/responsive-design-with-css3-media-queries
I can help you with the specific code in your new thread, once we sort out the other issue.