Creating Custom navigation in wordpress with sub menus

Here is your walker class

class Description_Walker extends Walker_Nav_Menu
{
     function start_lvl( &$output, $depth = 0, $args = array() ) {
        $indent = str_repeat("\t", $depth);
        $output .= "\n$indent<nav class="dropdown-list w-dropdown-list">\n";
    }

    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 )
    {
        $classes = empty($item->classes) ? array () : (array) $item->classes;
        $class_names = join(' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) );
        !empty ( $class_names ) and $class_names=" class="". esc_attr( $class_names ) . '"';
        $output .= "";
        $attributes="";
        !empty( $item->attr_title ) and $attributes .= ' title="'  . esc_attr( $item->attr_title ) .'"';
        !empty( $item->target ) and $attributes .= ' target="' . esc_attr( $item->target     ) .'"';
        !empty( $item->xfn ) and $attributes .= ' rel="'    . esc_attr( $item->xfn        ) .'"';
        !empty( $item->url ) and $attributes .= ' href="'   . esc_attr( $item->url        ) .'"';
        $title = apply_filters( 'the_title', $item->title, $item->ID );
        $item_output = $args->before;
        $wraper = ($args->walker->has_children) ? '<div  class="toggle">':'';
        $item_output.= $wraper
                    . "<a $attributes $class_names>"
                    . $args->link_before
                    . $title
                    . '</a>';
         $wraper_end = ($args->walker->has_children) ? '</div>':'';
         $item_output.=  $wraper_end
                    . $args->link_after
                    . $args->after;
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
    }





    function end_lvl( &$output, $depth = 0, $args = array() ) {
        $indent = str_repeat("\t", $depth);
        $output .= "$indent</nav>\n";
    }

}

and this is code for header.php i hope you’ve registered Primary menu..

 wp_nav_menu( array('menu' => 'Main', 'theme_location' => 'Primary','container' => '', 'items_wrap' => '<nav>%3$s</nav>' , 'walker' => new Description_Walker()));