How to display child pages instead of parent page in menu bar

Hi,

For some reason, in my site only the menu 'Afzonderlijke werken' (my site is in Dutch) is displayed in full; the other category menu's display only the parent page, which is already a duplicate of the menu title (displayed in black capitals).

I am not sure why this is, but I would like to have the child pages immediately under the parent page to be displayed. I hope I am making myself clear. Please let me give an example:

The menu item 'KRITIEKEN' has the link 'Kritieken' below it (which is an unnecessary repetition of the title). If you click on it, 8 child pages appear in the menu. Those are the ones I would like to have displayed from the outset, i.e. when visitors land on my site. How can I arrange for that?

Thank you very much for your response!

Kindly,

Rutger