Need help with custom menu-walker

My PHP skills are poor so i can’t do it myself so maybe here you can help me.
What i want to do is to apply off-canvas from this codepen https://codepen.io/designsoutheast/pen/ZYERGo to JointsWP theme. Both are Foundation 5 based but JointsWP display off-canvas in different multi-level menu. ( see https://foundation.zurb.com/docs/components/offcanvas.html#off-canvas-multilevel-menu

And this is menu-walker i need to edit

class Offcanvas_Walker extends Walker_Nav_Menu {
	function display_element( $element, &$children_elements, $max_depth, $depth = 0, $args, &$output ) {
		$element->has_children = ! empty( $children_elements[ $element->ID ] );
		$element->classes[] = ( $element->current || $element->current_item_ancestor ) ? 'active' : '';
		$element->classes[] = ( $element->has_children && 1 !== $max_depth ) ? 'has-submenu' : '';
		parent::display_element( $element, $children_elements, $max_depth, $depth, $args, $output );
	}
	function start_el( &$output, $object, $depth = 0, $args = array(), $current_object_id = 0 ) {
		$item_html = '';
		parent::start_el( $item_html, $object, $depth, $args );
		$classes = empty( $object->classes ) ? array() : (array) $object->classes;
		if ( in_array( 'label', $classes ) ) {
			$item_html = preg_replace( '/<a[^>]*>(.*)<\/a>/iU', '<label>$1</label>', $item_html );
		}
		$output .= $item_html;
	}
	function start_lvl( &$output, $depth = 0, $args = array() ) {
		$output .= "\n<ul class=\"left-submenu\">\n<li class=\"back\"><a href=\"#\">". __( 'Back', 'jointstheme' ) ."</a></li>\n";
	}
}

It would be nice if i could only replace classes but not all of them are would be generated in the same place (has-submenu in div and off-canvas-submenu-call need to be in a href).