Profile: Alessandro

if ( ! function_exists( 'ref_enqueue_main_stylesheet' ) ) {
    function ref_enqueue_main_stylesheet() {
        if ( ! is_admin() ) {
            wp_enqueue_style( 'main', get_template_directory_uri() . '/style.css', array(), null );
            wp_enqueue_style( 'child-style', get_stylesheet_directory_uri() . '/style.css', array(), null );
            wp_deregister_style( 'bootstrap_css' );
            wp_deregister_script( 'wpbootstrap_bootstrap_js' );
            wp_register_style( 'bootstrap_css', 'path/to/bootstrap.4.css' , array(), null );
            wp_register_script( 'wpbootstrap_bootstrap_js', 'path/to/bootstrap.4.js', array( 'jquery' ), null, true );
            wp_enqueue_style( 'bootstrap_css' );
            wp_enqueue_script( 'wpbootstrap_bootstrap_js' );
        }
    }
    add_action( 'wp_enqueue_scripts', 'ref_enqueue_main_stylesheet', 100 );
}