Welcome to Kali-Linux

https://kali.training/topic/configuring-the-network/

NETWORK

service wicd stop
service network-manager restart
ifconfig -a

/etc/network/hostname
invoke-rc.d hostname.sh start
/etc/network/interface
/etc/network/interfaces
/etc/init.d/networking-restart
service networking restart
update-rc.d networking enable
/etc/resolv.conf

Monitor Mode:

ifconfig wlan1 down
ifconfig wlan1 mode monitor
ifconfig wlan1 up
iwconfig

Wlan WPS check:

wash -i wlan1mon
reaver -i wlan1mon -c CHANNEL -b BSSID -v
(-d 5 = delay in Sekunden)

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

My WiFi went down

Also, the GUI showed that wlan0, my WiFi interface, was Unmanaged. So I looked at

cat /etc/NetworkManager/NetworkManager.conf

and realized there was a line saying

unmanaged-devices = interface-name:wlan0

I used NANO to remove the interface from the unmanaged list, did

systemctl restart NetworkManager.service && 
systemctl restart network-manager.service && 
systemctl restart wpa_supplicant.service, 

and it worked fine.