Hustle Plugin Error after Installation

Hi Guys, I've installed your plugin Hustle and straight after that my website stopped working..

"Fatal error: Cannot redeclare class Mailchimp_Folders in /home/obsession4fashio/public_html/wp-content/plugins/wr-contactform/addons/mailchimp/api/Mailchimp/Folders.php on line 3"

This is what has happened.

I would appreciate your help.