Main menu page not viewing with childs

Hi,
been busy with the Customizr Theme for a couple of days. I’m stuck at one point that it’s not possible to see the page that is a main menu level as soon as I have linked a child or grandchild under it. As a single page only, it’s okay.
Another them I’ve used earlier – Admired – I didn’t had any problem.

Please help because I need to go further!

Otherwise, a great theme so far.

greets Michel