Hi David,
Sorry for the delayed reply, please give us a chance to help you. The header that we are seeing on this site (https://engenius.eu/
) is actually a straight forward and easy to do even for beginners, as you can see that site has a Navigation Inline on desktop and a Navigation Collapse on mobile.
The trick of showing only one navigation and hiding the other on certain screen size is achieved by utilizing the Hide During Breakpoints option, all elements have this Hide During Breakpoints option so you can easily apply this.
As you can see on this screenshot you have 5 screen sizes option (XL, L, M, SM, XS). You just select on which screen size you want the element to be hidden, so that is Navigation Collapse will be hidden on XL, L, and M (hide on desktop), while the Navigation Inline will be hidden on SM and XS (hide on mobile).
For now, please focus on these three things to easily understand how this works. Forget about the layered menu that you’re referring for now as I think that is causing you the confusion.
Let us know if there is still something that is not clear.
Cheers!