Menu does not work

Hi,

Few questions about the menu on my website http://www.dilemmaboek.nl.

1 I have added sveral submenu’s, but on the site they won’t show. Not when I hover over the main menu items, nor when I click.

2 When I narrow down the browser to watch the site in a mobile phone setup, or when I look at the site on my mobile phone, the menu is moved to behind that menu icon with three small horizontal stripes. Yet when I click that Icon, the menu does not unfold, pop up or scroll down. Nothing happens, which means that the 30% of my visitors who use their mobile devices can’t do anything or go anywhere on the site.

Does anyone know how to solve these issues? Do I have to change or add something in my child theme?

I am relatively new when it comes to working with WP, and this is the first time I work with this theme. So maybe I overlook the obvious. Anyway, all help is welcome. Thanx!