For example I was having slow speed with Intel Centrino Advanced-N 6205 (you can see adapter model with lspci|grep -i net). My speed went from 5MiB/s to 24MiB/s so 5X speedup!
Try this:
sudo mkdir /etc/modprobe.d
sudo cp /usr/lib64/modprobe.d/20-iwlwifi.conf /etc/modprobe.d/
add a new line to the config file as sudo: options iwlwifi 11n_disable=8
sudo gedit /etc/modprobe.d/20-iwlwifi.conf
options iwlwifi 11n_disable=8
and save & reboot
If you are having bad network speed with WiFi, use ethernet 
Justin And preferably via 40Gbps sfp+ fiber media just to be sure.. 
E. On the more serious note my laptop is old HP Elitebook. I'm not sure if that is the best performance wifi adapter for that laptop as those things have damn vendor specific lock downs in bios/uefi fw, also iirc Lenovo has too so there is unfortunately some restrictions what wifi nic you can pop up to these and might be limited for options because of this too 
I'm so lazy to deal with wifi I have a range extender plugged via Ethernet to my PC. Works
