hackwifi is not a command.I believe it is just explaining what this command “besside-ng wlan0” do. “besside-ng wlan0” is the command.
The command syntax should be - besside-ng options interface
besside-ng -W wlan0
You can check out the Besside-ng usage here - https://www.aircrack-ng.org/doku.php?id=besside-ng
probably u didnt save the alias to alias file ,if u dont save it bash execute them only when bash is active when u close it they will be deleted so save them to alias file.
or chek if u have installed app.