Whonix Gateway eth0 static ip

Hello guys,
I just tried to change the IP of eth0 to use an internal network instead of NAT.
Here is the tutorial i used: How to Set a Static IP Address in Linux - Daniel Miessler

My settings on the Gateway:
IP Address:
Subnet Mask:
Default Gateway:

My settings on the other OS, which should share the internet connection:
IP Address:

To find these settings I watched this tutorial: - YouTube

After I changed the settings the Workspace disconnected from the Internet. Can someone help me out?

My gole is to have an OS as an pre-gateway.