Laravel Mix Purge Css

Greeting every one I have a theme that I bought from ThemeForest the problem is that there is a lot of unused CSS which reduces the performance of the theme so I decided to use purge CSS on bootstrap CSS file and style CSS file but when I used it the plugins in the theme stop working I guess that because purge CSS removed the classes of this plugins and consider it as unused so my question is how can i reduce unused CSS by purge or any other method