"firmware-linux-free" Driver for Fritz WLAN Stick

I have a WLAN Stick called “Avm Fritz! WLAN USB Stick N v2”.
The driver was installed automatically from OSMC - nice.

But the connection speed is very low (maximum 16Mbit). With Ethernet I get 35-40Mbit with the pi (with Windows PC 45-50Mbit). I’ve tried other WLAN devices and with them I get at the same position and distance 35-40Mbit.

I’ve read the hint, that I should install the “firmware-linux-free” driver and then it should work better. I did this with the “apt-get” command and I got a success. But the speed is the same. So I’m wondering, if the driver is not loaded or if there is another problem with the combination of pi + osmc + my wlan stick?

When i plug the stick in another device, the connection speed is fine (35-40Mbit).