So I recently moved one floor up forcing me to use a range extender since our LAN-Ports don't work properly. My current problem is, that my phone has the normal download speed i am used to have on my home wifi, but my PC only gets like 1 Mb/s of download speed, which is basically nothing. Before that, I was able to easily get 120+ Mb/s of download speed on both devices, now only my phone has a download speed higher than 1 Mb/s.
Load times are also differnet on PC. 

Anyone knows, why this is the way it is?
Things I already checked and did:
  - My PC supports 5 GHz Wifi 
  - Other devices (such as my tablet) connected to the wifi also get around 80-100 Mb/s 
  - Reset the connection, disconnected all devices and only connected my PC, same effect.