Prestashop working very slow, fine tune settings

One of our website which runs on prestahop is loading very slow, this needs to be fixed as none of us are expert in servers and php. We need someone who has good experience in prestashop's technical side, php and servers. The freelancer will have to work on our pc via any remote desktop software and solve all issues and make the front end and back end lightning quick. The freelancer would also have to suggest any other changes in modules if required. If this association works well we may hire the same freelance for our other eCommerce websites too.