Mobile Navbar Menu Disappeared, but assets are still there

Hello all,

This is my first website.
Last night I made a lot of progress on my site, I stayed up pretty late.
At the end of the night I did a full click through of the site only to notice my tablet and smaller navbars were broken, the text and hamburger menus had disappeared.

I am not too sure about how to get them back and any help would be greatly appreciated.

Here is my site share link