#wifi

I did a factory reset on my wifi systems and now I'm only connecting at 174 Mbps instead of 867 Mbps. I changed nothing on my Linux system. I changed the 5 GHz wifi from an 80 MHz channel to a 20 MHz channel. iwlist says the wifi offers 780 Mbps, but I can't seem to connect at that speed...

Hello! I installed BackBox Linux today but its wifi doesn't work! It says no devices available and something like this. what shoud I do? Thank You