Not getting full connection bandwidth :(

My WiFi Adapter: D-Link DWA-131 REV B
Driver: official D-Link DWA-131 REV E released for OSX 10.11
My SO: OSX 10.12.3

Speedtest (same host selected) runs:
- With the USB Adapter: 10mbps download
- With Android USB Tethering: 50mbps download

Is there anything i can do to improve my connection speed while using my USB Adapter?

EDIT: everything works fine when i'm using my USB Adapter, nice ping on games, no crashes, no freezes, nothing, except for not getting all...

Not getting full connection bandwidth