Items won't fit next to each other

Hey,
I’ve been trying to get this to work but without any luck. As you can see here: http://scheppersonline.be/
under the menu “studenten” and “over ons” there are two items “Agenda” and “Chamilo” but they won’t fit next to each other. I tried placing them next to each other with 4 columns, 8 columns etc… But they always appear underneath each other. Could someone help me?

Greetings
Bram

https://wordpress.org/plugins/megamenu/