Native Theme

Add this code into function.php of your child theme.

Please make all changes to the child theme files, and do not add the code directly to the theme files, otherwise after updating the theme your fixes will be lost

function.php

// ------------------------------------------------------
//         Groovy Menu plugin integration
// ------------------------------------------------------
if ( ! function_exists( 'gm_child_show_groovy_menu' ) ) {
	function gm_child_show_groovy_menu() {

		// Work only if Groovy Menu plugin active.
		if ( function_exists( 'groovy_menu' ) ) {

			// Override DFD header clas by empty class.
			if ( ! class_exists( 'Dfd_Header_Constructor' ) ) {
				class Dfd_Header_Constructor {
					function __construct() {
						// empty...
					}
				}
			}

			// Output Groovy Menu.
			groovy_menu();
		}
	}
}

// Add action for early BODY start.
add_action( 'dfd_after_body_start', 'gm_child_show_groovy_menu', 5 );