please add a feature key that would allow me to postpone a game in case i want another friend to join after the round is finished. Also, could you make it possible to add an option to encrease or decrease the amount of time between waiting for the next round by adding a feature to do that? Other than that, the game is fantastic.

Nobody can join your game between two rounds. If you want someone to join your game, you must stop it (with the X key) and start it fresh again when he/she is ready.

It's usually not desirable that someone joins a game between two rounds without restarting. It is totally unfair for everybody.

It isn't fair for other players for example if everybody has around 200 points and the new coming guy starts at 0. He/she has much bigger chances to win.
In the opposite sens, it would also be unfair if the new player started with a given number of points different than 0, for example by taking the average score of other players or any other similar ways of deriving an initial score based on what the others did so far. Why should you start with something while you just arrived and did nothing ?

This type of reasonning is true for all the games available on the playroom. So if you want to add another player, everybody should start fresh again at 0 points in a totally new game.

Now for the postponing feature, given that everybody is already playing and ready to continue, it doesn't make much sens. If you want to pause a game and continue later, you have the save and restore feature.