Bad SQL queries cause a low site performance.

The project is about an online shop, built in Joomla 2.5.4 and Virtuemart 2.0.6 with a template from Templatemonsters.com. The database includes 15.000 products and 1350 categories, in 3 languages. Issues: First page opens in about 15 to 35 secs. Other pages in about 16 seconds. There are some sql queries that seem to load the whole database sometimes and look like they are in a loop, causing very low performance, timeouts and server overloads. Notice: Google has cached some pages that have expired. Although they crawl the server using the cached links that are no longer exist. While this happens, most times the program lands to a page that reads all the records, causing server overload as well. Need: Find and replace the sql queries to avoid useless loads. Improve better performance using page caching, page compression, css & js compression, site optimization. Get rid of bad crawler requests. Main page [login to view URL] (this has 15.000 products - 500 published) A copy of the site at [login to view URL] (this has 15.000 products - all published - not cached by google's bot yet). (I am terribly sorry for any inconvenience in an older post according to the project's budget. This is my first touch with this site :), so please accept my appologize.)