Hello 

Which T-Mobile modem do you have and if you use a cable is the speed than okay?

Where is the WiFi repeater located?

A default wifi repeater is a bad unit. It devide the speed by half and you have no clue if the device attach to it. T-mobile got a more professionel solution. It is a wifi Mesh system.

Thanks for your reply Waqqas. I found these information on the modem: T-mobile Home Gateway, HG659. The repeater is more or less in the middle of our apartment.

With cable, the speed is much better. That’s why I guess it should be problem with wifi signal.

Thanks for your reply Eric. I checked with speedtest and the speed is not even one-third. I know the option using Wifipoint but that probably the last option. It makes more sense with a big house. I more or less expect the router (+wifi extender) to work properly in an apartment.

In an appartement building are already many other wifi hotspots and they all interfear with each other. 

The wifi extender is creating a more negative signal inside. This device receives from your device and then retransmits on the same frequenty. 

There are some things you can try first. See this page 

Thanks Eric. That’s a good source. Will see how it goes.

@tinnguyen299 

Is it possible to set the WiFi repeater in Acces Point mode with the WiFi of the modem switched off? Good isolation of the floor and walls could also play a factor.

Does the WiFi speed increase when near the repeater?

@Waqqas Thanks for your questions. I have just checked more thoroughly.​​​​​​ Coming close to the repeater increases the internet strength very slightly (according to speedtest). I have now a single band repeater  (tplink wa850re). Making it an Access Point is not possible since it quires to have wire connection to the T-mobile router.

Interesting (but unfortunate) thing is that when I move the extender next to the router, the speed doesn’t seem to crease much. I guess I am having a bad repeater.