Hi Jeroen,
Your problem might have been solved by now but just in case it isn’t.
The reason the Mx Studio screenshot is showing the 4 columns in a 2x2 orientation is because the tablet view mode is being used. A layout grid will reorder its columns into rows as the screen its on get smaller.
You can activate this tablet view in the design mode of your studio pro by clicking the small tablet icon thats just above the dark blue topbar of the page in your screenshot.
Try also playing around with the phone view and see what happens.
Hope this helps!