Hello @cyberando,
Thanks for writing to us.
I checked you given page URL since your page content is less just because of that the page height is looking small on large screens. I would suggest you add a custom class in the section and then add this custom CSS under Pro—>Theme option —>CSS

.x-section.section-height {
height: 100vh;
}
Please feel free to change the class name. Please make sure if you change the class name you need to change the class name in the code as well.
I checked your site’s menu it seems that the menu is working fine. It might me cache issue at your end I would suggest you clear your browser and then check it again. Please have a look at the given screenshot below.
The purpose of providing the custom CSS to show you how to add CSS code to your site. Writing custom CSS is outside the scope of our theme support. If you need more customization, you need to learn CSS and learn how to use the browser’s element inspector.
Hope it helps you.
Thanks