I see, thank you for your help. I tried to remove `iwlwifi-6050-5.ucode` from `/lib/firmare/` but it broke the ability to use Wi-Fi card as a hotspot which is important for me, but otherwise, it worked better. But I found that adding `options iwlwifi bt_coex_active=0 swcrypto=1 11n_disable=8` to `/etc/modprobe.d/50-iwl3945.conf` significantly improved the speed (to same speed as in Windows) but the hotspot still has some speed drops. (The options are described in `$modinfo iwlwifi`) I maybe try ndiswrapper later but it's good now (except the hotspot which works well in Windows).