Thanks for the answer. The travel speed is set to 150 and the acceleration settings are always the same defaults. Netfabb pushes the head around much faster even. If i run the bed leveling wizard in Cura and set the nozzle to literally touch the buildplate in all corners, i notice two things: when the print head comes to calibrating the back corner on the right, it doesn't move in parallel to the bed but rather moves noticeably "inward". When I then print the test square around the bed to finalize the process, it will go from corner to corner but only touches the buildplate slightly in each corner and the connections in between are not attached to the plate. I'm not sure, but it seems to me, like this was not the behavior at start when I bought it a few weeks back. It seems like all this "weirdness" only started after I made my first print attempt with Sli3er. During that print the printer made horrible noises, that sounded like some gearbox somewhere was tortured to death. Until I noticed that it had mad speed settings, which caused some strain on the printer. Nonetheless, the only issue is, that the first layer doesn't even touch the plate. If i turn the z-screw until the nozzle hits the plate during the skirt-print, I end up with a, as-ever flawless print.