Error 404 / Contact Page Disappeared

1. I need assistance to make the navigation menu work.
(If you click the Buttons/hyperlink on the Homepage.)
– The page bounces back
– Contact us page shows the Homepage
Note: I can see the contact page design in Pages Editor. I’ve tried Duplicating the Page and Publishing to no avail. https://drive.google.com/file/d/1U28zVJOTjGnZ4DCWNfXhLKPq1hF05VwL/view?usp=share_link I noticed both contact pages are published and nothing is showing up as designed. I’ve never had a problem with navigation and basic contact page with other platforms in the past.
https://drive.google.com/file/d/18BMj48cV3kwXIwpRLABu–ugyMX8MXcs/view?usp=share_link

2. The Homepage Shows 404 if you click a button or navigation (Contact Us)
https://drive.google.com/file/d/1b4EJi_3hibzmzlRR-a0EeTCL2DhA6g9J/view?usp=share_link

3. Website https://docs.google.com/document/d/18qRtKEHgnPrhMvMlb4q27GFxst9Z3jHJc9ilMKMO6U0/edit?usp=sharing

I am not sure what is wrong? Should I delete the entire website and start anew or can this be fixed? Any advice to the Developer that sent me the message below?

Developer Note: The whole entire routing system is not working and a lot of that functionality is under the hood of the wordpress site. I believe the way the router is setup and the theme is breaking when trying to go to another page. I did go through tutorials online to fix this issue, but they did not work. I will finish up redoing parts of the site with a different routing system to fix the pages and links.