Forum on Mobile
please check it on this (our) forum, you may have site specific problems. Then let us know what is the browser name and leave some screenshots.
Could you please turn on the menu and put some widget?
Here is some tip for the menu: https://wpforo.com/community/faq/menu-disappeared-after-changing-theme/
Some css conflicts with wpForo and removes categories on small screens. Also please deactivate all plugins one by one and check it after each plugin deactivation. Then we'll check the theme.