Having issue in minifying CSS files

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There is an issue with the page lading time and for that I want minify my css and JavaScript files and I want to know that if I use any plugin for this process.
Then these changes remain in my site after theme and plugin updates or not or is there any other method to minify my CSS files which is long lasting.
Thanks

• This topic was modified 5 years, 6 months ago by Steven Stern (sterndata).

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