Urgent fix for wordpress site - URL issue

A freelancer from here was doing a Performance update for my WordPress site but unfortunately he has changed the URLs for a set of pages And he has applied a 301 redirect from the old URL to the new URL.

I need to :
- revert the URLs back to the original URLs,
- switch the 301 redirect back to the correct URL structure.
- ensure the internal links are pointing to the correct URL structure (there are no hardcoded links)

This is an urgent fix before Google crawls the old/new URLs - only apply if you can resolve this within 1 hour.

Thanks