Is there some sort of clever hack of achieving that, because I did not find anything. I have a 27" Mac and everything is still kind of huge.
No - you get two windows in the current implementation. One on the left and one on the right.
I suppose the notification center slide over could be considered a "third window" but you can't put an application window there - it's just a system tray of sorts.
I would look at a program like Divvy on the Mac App Store for customizing a workspace with multiple tiled windows. It's not split view, but it's far more flexible and able to make use of the 27 inch display space to quite a granular basis.
Hopefully something like this becomes a standard Mac feature. I like the split screen feature, but sometimes I want/need more than two screens. I found a pretty good solution on the Apps store that will let you have split screen, one window half/two in quarters, or 4 windows is quarters. It is called Magnet. Works great on OSx Sierra, and is much cheaper than Divvy. Here's the link!
@Harry is actually providing a very good recommendation without being very specific about it.
Spectacle does (almost) exactly what you're looking for. It's not strictly speaking split view, but it allows you to split windows between the three third of the screen via simple shortcuts:
In addition, it's free and open-source.
Me from the future here; I ended up settling for Magnet
It has nice logical shortcuts to snap windows to quarters, halves and thirds of the screen and supports dragging to the edges of the screen, like in Windows. Easily worth the 1.09€ for me.