First of all, please remove module suffix bigspaces from both modules element. Also remove from override.css style that moves .box element up. Then write back.
So I'd delete every .box from override.cs. Also I'd delete the "bigspaces" in the Modules <Mainbody content> and <Mainbody sidebar> (i'd deactivate the this). Now it looks much better. Only the Modul <Slideshow> fits not. But Tanks until now!!!