[Solved] Connect one router to another to make new network?

I am trying to plan out a network setup, that will let me use my primary work desktop in a separate network from a test network that will contain servers in a domain with test machines.

I’m in a dorm with one Ethernet jack that gets assigned 1 IP from the university. Right now I just have a basic consumer type dlink router connected to it, and then my primary desktop is connected to that, and a laptop is connected wirelessly.

I’m wondering if I got another router, and connected it’s wan port to a regular port on my main router, if that would let me create a 2nd separate network, that I could then create a actual domain with test servers, and a separate IP structure that would not conflict or even be able to directly access my primary desktop PC. This is graphically what I am thinking:

ok, so if I do that, and create a domain and have a domain controller and dns running on my test server, my primary desktop that is in the different subnet will still be able to function fine without being in the domain right?

Also will the computers connected to the 2 different routers be able to communicate at all?, like say I want to run a virtual machine on my primary desktop in the other subnet, would I be able to join a virtual machine that is hosted on my primary desktop to the actual domain that my test server creates, by changing the subset that it is in?