wp super cache serious problem

I was using wp super cache for a long time but then decided I might try a new cache plugin, big mistake. when I deleted this plugin it left things behind which I have read is a common problem with the plugin.

Now, when I try and install a different plugin I receive errors, and I even receive errors when I try and install wp super cache again.

can anyone give me advice on how to solve this issue as now, when I install a cache plugin it does not make any difference to my website speed as it is not properly working

The page I need help with: [log in to see the link]