The couple in the first room is actually your geography teacher and his spouse, and the beautiful girl in the second room is actually what you subconsciously want to be, and also the representative of your heart. You in the third room are the embodiment of yourself in real life, and that old woman may be the embodiment of your self-protection consciousness. Because you like the geography teacher and want to associate with him, you dream that a man betrays his wife and trysts with a girl. But your consciousness knows that this is wrong, so the beautiful girl in your dream appears as "someone else", not yourself, so you will wake up the next day and appear in the second room where men and women meet. It is also because you know that your feelings for teachers will not be recognized and recognized by the society and most people, and you are afraid of being criticized and rejected, so you will dream that your wife has found out that men and women are cheating (and your wife is the representative of your social moral consciousness). In the dream, you wake up and hug your grandma because you know that everything is an illusion, and grandma's hug is that you are comforting yourself. But you are unwilling, and you don't want such a result, so you dreamed that grandma gave you her brains to drink, which is a very subtle way of self-venting.
Well, that's just my own speculation about this dream. Please don't take it amiss if there is anything wrong ~