( ! ) Fatal error: Uncaught Error - Cannot access my local website anymore - help!

I work on the website 2 days ago and it was perfectly working and then tonight when I tried to log in, the message above just showed up

( ! ) Fatal error: Uncaught Error: Call to undefined function et_get_option() … with a link to where the files are and it seems to deal with a php file but actually didn’t touch it at all since I really don’t know how to deal with it. And now I’m being completely lost … Please can someone help me with that issue ? What does it mean ?
I can’t access anything …