We have had a site built by another provider, but it hasn't been working in any hosting environment but his. Your job is to properly connect it to the database and try to fix it.
Then, we need to review site, make necessary changes, etc. The site is PHP-powered, features a mysql database (not connecting), and also a login for employees (which you may need to help with).
Providers should know what they're doing and be willing to finish this job ASAP.