Fatal Error Message

Try replacing your wp-admin folder. That should correct the issue.

If not, what’s your URL?

You’ll want to do it through the FTP. You can find your FTP login credentials through your host.

I tried filling out your contact form to help you more. Hopefully you got that.

You’ll need an FTP program like Filezilla:
https://filezilla-project.org/

In your host, you have an FTP login somewhere. That would be entered into the appropriate area in Filezilla. Go through your public_html folder and find the wp-admin folder. That needs to be replaced.