At the end Erfindercamp when @Minirevollo and Rolf we’re building a door I finished the Standard Frame out of 6x6 (6cm by 6cm) thick studs. In the instructions, they always talk about 2x4 and if you convert that into cm it should be 5,08 cm by 10,16 cm. So I thought a 6x6 beam is ok but it was too big because a normal 2x4 beam is actually 1,5 x 3,5 inches which means 3,81cm x 8,89 cm.
So the 6 cm screws that came with the maslow were to short to combine the two beams and I had to drill holes. The frame is ok but it is pretty difficult to unscrew the screws and some beams are not connect got as I drilled some holes not deep enough. So I will get bigger screws for the next time and buy the right beams.
In Germany there is no real equivalent for 2x4s that I could find in the shops online a60x90mm and also 40x90 mm.