I managed to wire everything up. It is not the best wire management, but it works. I added a LED-strip at the front for better looks and usability. The power supply and EinsyRambo are mounted under the 3d printer between the Z-slider and the printbed.

In the back, there are a power switch, a USB-port and a power connection + fuse.

First print :

The first prints are looking very promising. I printed the test cubes with a 0.2mm layer height.

On the other hand, the first layers are still pretty bad.
I lifted the printbed 6mm as I thought this would improve it, but it didn't.
Without a heated bed, the print adhesion ist not good, which could be a factor as well. The Z-slider has some flex which leads to some looseness in Z-direction. It is made out of 3mm Aluminum(7075), but it is still not rigid enough. I want to try to reinforce it, maybe this will help.