Noob: PUN Server Creation and MMO example

Hey photon-com!
I know about photon since yesterday and I cant stop reading everything you produced the last like 6 years.
After watching videos and reading through the docu I still got some understanding questions cause I am totaly new to networking.

What I want to do is to use PUN in Unity with a Central Custom Server for a mmo-like

1)
I downloaded the Photon Server SDK.
What I would like to do is to start the mmo Server (cause thats what I need) and learn from that example.
Sadly I got the working Clients but not Server Files, is the mmo Server up to date or is LoadBalancing the way to go?

2)
Do I understand it correct that I want to create a Server with the Photon Server SDK in C# and then I can use PUN (in normal unity editor) in combination of this Server?
So if I just use PUN standalone he connects to one of Photons Cloud Server, but with a Server from the SDK he kinds of forward to my Server ?

Thanks in advance,
have a nice week