Fatal Error PHP Message

Last night I switched my URL to something else and changed the nameservers. Today I logged in and it looks like this.

Last night I logged into my WP dashboard and tried to update to the newest version. I left it for a few minutes but it stopped loading so I closed the page.

Now I don’t know whether the nameservers just haven’t switched over yet or that I did something wrong by closing the page in the middle of the update, or that simply something else is going on.

The website can be found here. Also, I’m not able to login via /wp-admin.php. The same error appears.
Thank you.