HelpBittorrent problem

Just bought a new usb adapter: TP-Link TL-WN821N
I tested my download + upload speeds on Speedtest.net - The Global Broadband Speed Test and it give 51 Mbps download and 5 upload.
When I download GTA 4 on bittorent I get very slow download speeds, changing from 50 kB/s to 900 kB/s but with my old usb adapter I had 1 mB/s to 2.5 mB/s.

-Check your download speed at that site, limit download speed and upload speed by putting 80% of that. (eg.: 100mb -->80mb)
-Make sure you have more seeders than leechers

you obviously don't know how torrents work
the more seeders the faster the download
choose a torrent that has high seeders and a fair amount of leechers.