If the keeper falls down and cannot get up,
the team should take away the keeper for 30 seconds.
If the keeper can go back to the field immediately after 30 seconds,
the other two players continue the whole game and don’t need to go back to the Goal.
Only if the keeper can not go back near the goal over 30 seconds, one player on the field needs to go back and become the keeper?
Since two players go back to the goal, it usually takes more than 30 seconds.
There are two different things that have to be considered here. First, there is a specific robot that the team has to announce that plays the role of the goal keeper. This and only this robot has special protection in the goal area. If this robot suffers from a penalty, it still remains to be the goal keeper, even if it was taken out. After 30 seconds, it can re-enter from the touch line and walk back into the goal area. In the meantime, another robot can walk in the goal area and protect the goal, but it does not automatically become the goal keeper. So it is allowed in the goal area because no other robot is there at the same time, but without any special protection. If you want this robot to become the permanent goal keeper with special protection, this has to be announced by the team to the referee.
Does that answer your question?