IE doesn’t display website correctly

Hi,
Internet Explorer displays only half the page (https://www.dansdrift.nl/ddcms/cursussen), even IE11. No problem using other browsers.
I’m using Agama Blue, with additional style (flexbox). Everything is up to date.

How can I solve this problem with IE, f.e. using extra plugin?

thanks for help, best regards, Alice

The page I need help with: [log in to see the link]