Change variable in one player and not all

Hello, I am new to multiplayer video game development and I have a problem, I am making a video game in which it is a race that if you do not meet certain conditions your character loses, but if you reach the end you win, the problem that arises is that you do not I know how to do it so that when a player reaches the end these conditions are not applied to lose, I try it with a triggerbox and when it detects the player that a boolean variable is applied to true but it is changed to all the players, how do I could you solve? From already thank you very much.
Sorry for my English

Make the changes in the player state of the specific player.