Drop Down Menu Not Working – Custom Theme

So I used this website to build my theme:

https://www.onextrapixel.com/2011/03/08/how-to-code-a-wordpress-3-0-theme-from-scratch/

But my drop down menus aren’t working. They’re displaying, but they’re just showing everything all at once, not doing drop-down or anything.

On top of that, all “posts” and “pages” submissions fail, although the page & post do get created, it doesn’t finish going through the post process.

I could really use help. If you need me to create you an account so you can poke around, please let me know. Thanks!