Securing Apartment Wifi

As you say, you cannot change the settings of the router and it is not your device. So treat it as that: Not part of your network!

Buy yourself another router that connects to the one you are provided with using (preferably) a network cable or if not possible WiFi. Configure that to treat this connection as WAN (the Internet) and to create a different wifi network for you, where you connect your devices.

If you want, you can configure your new router to build a VPN connection and send all traffic through that. Downsides are, it costs money and latency and bandwidth are worse. You shouldn't send anything unencrypted via the internet anyway, so I would consider that optional.

The important part is:

  • None of your devices should be connected to the provided router and wifi, only to your new router.
  • your new router should see the network of the provided router as external network
  • a device connected to the provided network shouldn't be able to access any device in your internal network.