Dedicated Web Server Going VERY SLOW - Needs to be fixed ASAP - Server Admin / PHP/ / MYSQL

My server is going very slow and we need to fix it, The load is not too high and we dont have too many visitors, but the website still goes very slow. We do have a large MySQL database and a php shopping cart which could be the issue, or maybe it is server settings. We are not sure. We need someone to diagnose the issue and be able to fix it. If you are an expert in server management, php, mysql, then please apply here, this is a urgent task and I need it completed quickly. OS on server is Centos. Once you bid I can show you website which goes very slow or we can talk more. I want to hire for this today.