plugin destroed my theme

I put this plugin on website. immediately i saw that in every browser, it just shrink my template. i deactivate it, even deleted it but the problem is still here. the site seems awful. please help. what files do you believe that your plugin effects? iam searching all over style files but i cant find any weird change. perhaps is something that iam doing wrong. plz help me.

https://wordpress.org/plugins/wp-responsive-menu/