Need Drupal Expert to fix Simple Drupal Site Bugs/Errors

Our site [login to view URL] was built on Drupal last year, but has begin to load extremely slow and now generates 500 Internal Server Errors when I go to the system login page or other pages. [login to view URL] We need these errors fixed so the site runs smoothly, loads quickly, and generates no server errors. I am not sure what is wrong, but am confident it is a simple fix. I am willing to provide any information I can to help you assess your bid amount. The maximum bid is $100, although it is possible this is a very easy fix, so please submit reasoning for your bid amount. Additional Information: The site slowed down over time and errors became more frequent.