Speed up OpenCart Website thats currently slow

Hi Guys and Girls, Currently have an opencart site with a theme on it which is very heavy. I love the look of the site and the SEO capabilities that it has (which aren't used currently as not loaded the full catalogue.) I require someone to get this site running very fast for me with no load errors and also look at the mobile version of the site which is currently turned off as this wouldn't work. The theme used is OpenCartWorks. The website is [login to view URL] I require the successful applicant to send me a full review of the errors on the site and what you propose to do to resolve this. I need a fixed price for EVERYTHING so that i can get this site working for me. Need realistic time scales as well. Many Thanks