Airmon-ng not working, how to fix?

Question

linux

For Nethunter, I used Termux on an Honor 8A phone, pinged the Internet, opened airmon-ng:

┌──(rootlocalhost)-[~]
└─# airmon-ng start wlan0                             
ls: cannot access '/sys/class/net': No such file or directory
Error: /proc must be mounted
  To mount /proc at boot you need an /etc/fstab line like:
      proc   /proc   proc    defaults
  In the meantime, run "mount proc /proc -t proc"

Requested device "wlan0" does not exist.
Run /usr/sbin/airmon-ng without any arguments to see available interfaces