Presentation page on mobile problems

My website looks fine on computers and tablets, but when it shrinks down to say an iPhone the presentation page goofs up. The pictures in the presentation load and move through the slides but below it seems the container doesn’t shrink to the right ratio and has an infinite loading circle. Any ideas?

Also, on the mobile the menu changes to a drop down menu which is great, but when you click on the parent links that have sub categories it bring you to a page that says “Not Found

Apologies, but the page you requested could not be found. Perhaps searching will help.”

Any ideas on how to stop someone from being able to click on the parent page? On the computer and tables in the menu you can’t click the parent tabs. Any help would be great thanks.
P.S.
I am new to php. Thanks