Hello,
The mobile menu does not support the mega menu blocks, you will have to create a separate menu for mobile.
You need to switch to the mobile view of the header and enter the mobile menu element and configure the showing categories: https://xtemos.com/docs/woodmart/header-builder/header-responsive-settings/ and https://xtemos.com/docs/woodmart/adding-menu-site/
We recommend WPML it is 100% compatible.
If you are going to change the PHP of the theme, you will need the child theme, if you are not going, you do not need it. it.
Best Regards
.
