Clickable parent menu on mobile

Hi, recently I took over the management of an EE 2.5.3 website and I noticed that when I create a page with child pages I can easily click on these parent pages and show their content on a non-mobile device. If I switch to a mobile device and I navigate the menu then I cannot open a parent page but only click on it to view the child pages.

Is there a way to fix this so that I can view the parent page on a mobile device? The site in particular is www.tracegent.be.