ERR_NAME_NOT_RESOLVED after trying to change the local URL

Today i was finishing my first website and it was looking so cool, but i had not make a backup of the original files. I tried to change the local URL and, i don’t know why and how, a bug poped up for me, and then i cant access the site or /wp-admin anymore. The site loads and after a short time returns me this error:

I think it is some DB problem, but i don’t know how to fix it. I hope you guys can help me. Thank you!