Find your gateway:

$ netstat -r -n

Find you IP address:

$ ip addr

For giving the Raspberry Pi a static IP address. Open the interfaces file:

$ sudo nano /etc/network/interfaces

And change the file to:

 # interfaces(5) file used by ifup(8) and ifdown(8)
 
 # Please note that this file is written to be used with dhcpcd
 # For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'
 
 # Include files from /etc/network/interfaces.d:
 source-directory /etc/network/interfaces.d
 
 auto lo
 iface lo inet loopback
 
 # Ethernet
  auto eth0
  allow-hotplug eth0
  iface eth0 inet static
   address ???.???.???.???
   netmask 255.255.255.0
   gateway 194.95.203.1
 
 allow-hotplug wlan0
 iface wlan0 inet manual
  wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
 
 allow-hotplug wlan1
 iface wlan1 inet manual
  wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

Disable the DHCP-Client:

$ sudo service dhcpcd stop
$ sudo systemctl disable dhcpcd 

Reboot:

$ sudo reboot