Following our selection of latest high speed “Power-line Adapter” generating high speed WiFi over all floors:
I always recommend to distribute the internet signal over all floors via a so-called power-line network.
That setup has the advantage of no signal loss as it freshly generates a new WiFi signal at any point you wish (given an available/nearby power socket).
There are different products available at different price levels.
I definitely recommend our customers to take the DEVOLO Set as it is the most reliable, most stable, most secure and best product to configure your home WiFi. A good price/performance is giving you the devices from AVM called FRITZPowerline or even the FRITZRepeater in case you just want to extend the WiFi to a nearby room in your new flat. The most economic choice is the TP-LINK set which does the trick but needs to be rebooted (unplugged and re-plugged) in a regular basis to get seamless WiFi and stable speed.