Yes. The Storchenmühle is built solidly, i.e. concrete ceilings. If the WLAN router is downstairs in the living room, the son upstairs will curse because the reception is so bad, and the resident of the attic will have their face completely freeze. The absolute minimal solution for 3 floors is a network socket on the middle floor (ideally in the hallway at 2 meters height), either with POE or with a power outlet next to it: a WLAN repeater is then placed there. Plus another network socket next to the router, which will then serve the socket upstairs.
Even better would be an additional socket in the study. The router itself can be placed in the media corner, where you can connect TV etc. with cables.
Please make sure to have the socket upstairs and next to the router installed! And if at first there are only empty conduits to save around 200 euros initially, so you don't have to regret it later...
For a typical single-family house, I would consider 50 power outlets as a minimal standard, "usual" rather 70, and comfort from 90 upwards. The standard in many construction service specifications is rather 30 to 40 sockets... with a general contractor you can quickly sink a few thousand euros there.