Slow upload speed and T Mobile home Internet

I had the same problem. Turned out that the speedtest(.net) by Ookla is not reliable app to test the speed. It assumes that server with the fastest ping is the best server for the test, which is not the case. Mine was almost in another country. That's why upload so slow. (less that 1Mb/sec).

Change server manually to one that is closer to you geographically and you most likely Ookla will show the promsed 5-20 Mb/s. (don’t you think it’s still too little?, but anyway this is what T-Mobile says is an excellent speed).