Hello! Im trying to understand how p2p works in a multiplayer game (1vs1) with lobby.
If i am not wrong I noticed that if the owner of the lobby has a low upload rate, he will have some advantages and his opponent will have a really slow game. Am I right?
I would like to understand what can influence the game if I am hosting the lobby (only low upload rate of the owner? Download doesnt make any difference)?
What about if Im going to play as opponent and not as owner of the lobby. Is there something about me that can make my opponent suffer even if he is the owner of the lobby?

This is all dependent on the specifics of the game, and the specifics of the lobby implementation.

The “game browser” is almost never operated by “peers” – it's a centralized system that lets peers find each other.

Games that are “browsed” are typically “hosted” by someone. However, the “lobby” may live on that host, or it may live on the game browser, or it may live on some third service.

The network performance of the actual game host does of course matter – if the game wants to send more data than there is uplink available for the host, you will see packet loss.

Whether the “host” will also have a “ping advantage” depends on your game implementation. In the simplest games, the host player simply interacts directly in the “server” process; this will give the host a significant “ping” advantage. In more balanced games, the host plays a regular client, and “hosting” starts a second process on the host computer, which acts as the server, and the game client for the host actually adds a bit of artificial latency to “even the playing field.”

@hplus0603 I am talking about PES21. I saw that in some cases the host had many “advantages” like a more fluid game instead of his opponent. I also noticed that who was hosting didn't have such a bad connection, a normal one like 20download 5-6 upload, that's why i thought upload could have an adversely affect.
I would like to know if my opinion could be right (a low upload from the host can make the game more fluid for him), and if the download could make any difference like upload.

Whoever is hosting will see more load on their “upload” than their “download” if there are more than a total of two players in the game. Thus, the limiting factor for hosting will generally be “upload.”

Having a low upload won't make the game any smoother for the host, but it MAY make the game less smooth for others, if the amount of bandwidth used by the game would be bigger than what the host has available.