Combine and Minify CSS

function combine_css_files() {

    wp_enqueue_style('combined-styles', get_template_directory_uri() . '/css/combined.min.css', array(), null, 'all');

    // Dequeue individual files if they are now part of the combined file

    wp_dequeue_style('style-one');

    wp_dequeue_style('style-two');

}

add_action('wp_enqueue_scripts', 'combine_css_files');