Experience open cart and PHP developer needed to fix existing down website.

Developer needed to troubleshoot issue with a currently developed e-commerce site. The site was developed and customized using opencart and PHP script. Last week we were advised that there is an issue with the mySQL file and the website is down, we are unable to contact the original developer, we need the website up an running ASAP this should be an easy fix easily by an experienced developer. Developer must be comfortable troubleshooting and resolving issues.