Ok, this is what i get thusfar: The scaling could be off due to communication error with the TMC if you power up the board via USB first and then plug in the adapter. So the routine is plug in the the adapter first, then connect to the USB (in case of calibrating etc.) The garbeling of the text is a bug, but it does not affect the printer. Simply clicking the button will go to the other menu and redraw the screen. Done.

I have that, i was wondering if i needed to change that, but it is as described in the guide. No jumpers under the TMC boards, only one 'next' to it on the corresponding UART position. I noticed that I have this issue only when i plug in the powercord *after* the usb connection to my computer. I get this TMC communication error as well. However when i connect the powercord first and the usb second, the text on the display is garbled... might this be a bug in marlin?

I'm still struggling with the assembly and i'm afraid its not my incompetence. I have a massive wobble on the z-axis in the z-direction that i can't seem to fix. I've ordered a metal coupling, because the plastic one provided streches and compresses a lot. This stretching and compressing is largely due to how tight I made the guides of the gantry grip the vertical support. However if i loosen them a little bit i get a wobble in the x-y plane everytime the z-axis moves. I'm afraid i won't be able to a simple print anytime soon...