Dedicated server and Session problem

Hi i’m making a massive open world multiplayer online game and i’m new to networking so correct me anywhere that i’m wrong .

as far as i understood as long as i don’t want to use steam (high ping in my country) i have to use dedicated server with that -server - log command thing , and each server or each instance of game count as 1 session . and for connecting to that session i need "open : " and as long as each PC has only one IP i can only have one session in each PC . with that i’m sure i have understand something wrong because it is not efficient at all . for example if my game has 5,000 players online , and each 10 of them are in 1 session it would take 500 session and 500 PC so i’m sure i’m wrong somewhere .

so as long as i have to go with dedicated server what is your suggestion to me ? what i have to do if i want players to create sessions and all this stuff .

and a lot of my thoughts are coming from the answers of this question that i have asked before

Thanks for your responds in advance.

Clients don’t create sessions. Servers create sessions. Clients connect to them.

My advice is you should read and understand well Cedric ‘eXi’ Neukirchen’s Unreal Engine 4 Network Compendium pdf.

anyone please ? i read Cedric’s Documentation but i still have the same questions