WooCommerce Outlet Theme Menu Dropdown issue

I’m currently using Outlet theme by Woothemes.

when hovering over Smart Phones menu to view submenu, the sort by dropdown blocks it, making it hard to select anything below the dropdown.

https://ngpstoreusa.com/product-category/smart-phones

How do I make the submenu appear in FRONT of dort by dropdown option?
see below snapshot.

https://justpaste.it/u5rq

I had this problem before, and was resolved by adding this line in stylesheet. but after changing to outlet theme I think it got deleted. So I added this again to styles.css under theme customizer, but not working.

.woocommerce-ordering {
    z-index: 1 !important;
}

Please help me fix this.

Thank you!