Why is my product template leading to a 404 page?

[Mavreck12]

Need help with a big problem

Hello, I was trying to add a new page in my Shopify store for my new t-shirt line but the new pages were only duplicates of my previous one. I was directed to delete a certain code that was "supposed" to fix this issue... Now my product template is gone. Every time I click on any of my products it leads me to a 404 page not found.