Internet hangs as soon as you log in with a second laptop or PC? (Location Austria / Lower Austria)?

My friend and I have chosen from T-Mobile the 2nd Best Internet tariff.

If he is alone with PC on the Internet (and both are normally connected to the phone) it is not a problem. I can also on the phone while he zips wow wow, netflix streaming. But as soon as I log in with my PC or with the laptop (and surf the net only) the Internet hangs.

Does anyone know what you can do there? Or what that is?

We had before a 3Drei tariff, and thought it is on the tariff but apparently not quite…

What does the 2nd fastest line mean? That varies from region to region Do a speed test:

http://www.speedtest.net/...est.net/de

17 ping, 4.37 download, 11.43 upload (if only I'm logged in)
67 Ping, 5.18 Download, 13.74 Upload (if only he is logged in)
27 ping, 3.17 download and 7.71 upload. (if both are logged in)