Hello,

If you use mega menu blocks on the desktop, you will need to create an equal separate menu and assign it as mobile but without a mega menu. This menu can be multi-level.

Here is the comprehensive guide: https://www.wpbeginner.com/beginners-guide/how-to-add-navigation-menu-in-wordpress-beginners-guide/

If you have any questions please feel free to contact us.

Best Regards