When someone approaches you and says "你人生开挂！“, they are complimenting you!
So what does 人生开挂 (ren sheng kai gua) actually mean?
It is actually used to describe that a person's life is very smooth sailing, and doesn't have much problems in life. Even if problems arises, it can be easily solved and so, the person is able to live life without much pressure or effort. Usually used in a context of complimenting someone else and saying that they have reached the pinnacle of achievements.