downloaded a plugin cant delete

So, I downloaded a plugin called "PreSuffixManager" and it's messed up the server. I go to files and there is no "PreSuffixManager.jar" only PreSuffixManager so I hit the bin (delete) button and i restart my server and it's back! What do I do please help, I only have 1 week to solve it! Please help.

Yours,

Brainless Network. (Rosie)

it is still there

plus there is no PreSuffixManager.yml