so ... now there are pictures that show the situation. Both doors go through brick walls. The wooden door (a 3-layer pine board) hangs on a double T-beam. The white (partially still unfinished) door is made of honeycomb cardboard (I know, that is unusual. It is self-made and specially light).
However, I believe that these pictures are not very useful because I first want to experiment less with the suspension and sound transmission, but rather above all I am looking for a rail system that is quieter by itself. For example, I wonder if the significantly larger wheels in such visible systems (picture) are quieter (larger wheels = less "jerking" with inaccuracies)?
Bending all individual parts - including the doors - is not really appealing to me, but where it makes sense, I do it ....