How do I correctly combine the styles of third-party plugins with my theme's styles?

Question

css

I decided to optimize my site and started disabling plugin styles. I copied all the plugin styles to my theme's style.css styles, changed the image paths, and still the post from disabling the plugin does not work correctly (For example, the Revolution Slider plugin). What did I do wrong? Tell me please.
Here is my code:

add_action('wp_print_styles','remove_styles',100);
function remove_styles() {
wp_deregister_style('rs-plugin-settings');}

Answer 1

Here, try to do it with this plugin bwp-minify