"Safari can't connect to server"

I messed up. I stupidly changed the URL in my settings and then all of a sudden, a 404 Error message popped up and then I was unable to access my login, dashboard, website, any of it.
I tried following some directions from this link: https://codex.www.ads-software.com/Changing_The_Site_URL
and I entered in some of the codes on the basic text file it opened up in. It did not work, so I got rid of them.

This is what currently pops up when I try to access my website.

Safari cannot open page “localhost” because Safari can’t connect to the server “localhost”

I am using MAMP as my localhost and cannot figure this out.
Honestly, I do not do codes. I don’t really understand the language that’s used in the help forums. I’ve been trying and struggling with figuring this out. If someone could put it in easier terms for me so I don’t think I’ve lost the website forever, that would be great.

Thank you.