Hello,
I recently got into Linux and created the following setup:

Mint system with 2 ethernet cards (used as media system),
Windows 8 system connected to Mint system via ethernet.


The Mint system is connected directly to my router.
Since I only have one ethernet connection in my room I use the media system to provide Internet to my Windows system.

I used the networksetting "Share Internet connection" to make this possible.

Now I want to connect with a notebook which is connected to the router via wifi to the Windows system.
Is it possible to insert the windows system into the main network?

If not is it possible to route all packages on a specific port which go to/come from the mint system to the windows system on the same port.

please help me I am getting kind of frustrated right now

Assuming this is your setup

(router with wifi) ----- eth0 mint eth1 ---- win8

You could bridge eth0 and eth1. This would make win8 appear to be connected to the router as well.

This would be awesome
How can I do this and will the firt computer still be in the network? ( or even able to connect to the internet )
Can I have two diffrent ip´s for them?

yes:

router | set ip via isp's ifex
mint | ip via dhcp
win8 | ip via dhcp

should work smoothly....

I think mint is based on debian so this howto on bridging should work fine for you. It's a pretty straight forward process and an easy setup in the interfaces file so that it happens automatically.

https://wiki.debian.org/BridgeNetworkConnections

Only took me 2 Days (for a total linux newbie this is fast) but finally got it working

Had some really complex designs to make it work but sometimes simpler is better
Otherwise I now "fully" understand networking


In case anyone comes accross with the same problem this is my /etc/network/interface