my website keep goin down

I'm on a Dedicated Server

but when ever I run ads by google

if the site gets 20 to 100 people at the same time it do down and I get this error

The connection has timed out

The server is taking too long to respond.

    *   The site could be temporarily unavailable or too busy. Try again in a few
          moments.

    *   If you are unable to load any pages, check your computer's network
          connection.

    *   If your computer or network is protected by a firewall or proxy, make sure
          that Firefox is permitted to access the Web.

is it the script or the hosing company settings

I have no problem with Google ads / VPS but I still never had more than 50 users connected at the same time... Anyway I think that you could ask your host provider first. 

I get about 700 email, this is the email

Database error
Mysql error:

Debug backtrace:
Array