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()));