I am looking at ways to optimize the speed of a Wordpress website and found that there is a css file containing a ridiculous amount of useless css and was contributing to the site's very slow loading time. The CSS file in question is located on the server at /htdocs/wp-files/wp-content/themes/regency-child/cache/dynamics.css (Not sure if that is enough to ring a bell).
My question is how is this file generated and how could I alter what this file is containing, as most of it is a monstrous thousands of lines of unused code. Being able to clean up this file would dramatically improve performances.
Any help would be very appreciated.