I have used several plugins for website optimization. But they all corrupted the site. Can you recommend an optimized plugin compatible with the theme?
Before installing external plugins, did you check the optimization options available already in the Betheme?
You can find these options in Betheme -> Theme options -> Performance.
But if you need to use a plugin I cannot recommend any plugins other than the ones we support. You can find the list on this page, in the sidebar: