There has been a critical error on this website

Just after installing this WP Quiz plugin, I got the following message: “There has been a critical error on this website. Please check your site admin email inbox for instructions.” I’m still awaiting this email. In the meantime, I hope you will be able to help me uninstall the plugin. I get that message when I try to view installed plugins. It also prevents me from adding a new post. I can view the rest of the admin tools though.

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