What should I do about my love for a sixteen-year-old girl, when no one knows about this love except for me and Allah?

If the girl is religious and of good character, and you are capable of marriage, then we advise you to marry her, based on the Prophet's (peace be upon him) saying: "There is nothing better for two who love each other than marriage," and his urging to marry: "O young people, whoever among you can afford to marry, let him do so, for it helps him lower his gaze and guard his chastity." If marriage is not feasible, then turn your heart away from thinking about her and cut off your relationship with her. As for seeing her in a dream, it is merely a self-talk and has no consequence.