Prevent scrolling when mobile menu is open

I updated from sparkle to sitely after a long time.

I have two device layouts. One for desktop, one for mobile devices.
For mobile devices I use the hamburger menu.
Now, when my mobile menu at my android smartphone is open, I can still scroll the content behind the menu but not the menu itself.

https://www.inuri.de/aktuelles/uebersicht.php

How do I prevent the page from scrolling when the menu is open an can scroll in the menu itself?
Any suggestions.

Thanks.

Your menu is fixed to page top, so it’s always visible and active regardless of where a user is on your page. It also retracts when a user clicks on the page - it’s designed to do that to prevent the menu remaining open if no menu selection is made. If you want a mobile menu that prevents page scrolling, it’s better to create it as a pop-up and replace the drop-down menu with a hamburger icon, and have the pop-up menu trigger when the icon is tapped. By setting the pop-up as a modal pop-up, the background of your page will be dimmed while the menu is displaying - preventing users from scrolling.

Personally. I prefer to use pop-ups for mobile menus because they give you greater design flexibility. Even if your pop-up is a “fixed in window” type, you can make it cover substantially the whole mobile screen, thereby making page scrolling less likely. In the screenshot below, i’ve used a three-dot icon as the trigger for the pop-up menu:

And this is the menu when it’s opened:

As I say, this type of menu does give you greater design flexibility, and often requires a close icon to dismiss the menu if nothing is selected.