The stl model of the DIN rail bottom of the case by khschneider on Thingiverse was scaled down by a factor of 10 so I had to upscale it in Bambu Studio to 1000%. To make sure it has the correct size I used the original model of thehair on Thingiverse and placed the top of the case on the same build plate.

I used the following screws, I had laying around:

4 x M3X16 Countersunk Head Screw (to combine bottom and top of the case)
4 x 3x6 Countersunk Head Screw (to fix relay Board in the case)