WIn but Point doesn't increase

Hi everyone, I am just learning chess, and my rating is around 800, pretty bad hahah. I just won a game with opponent rating around 1150, and I checkmated him after like twenty or thirty steps. Yet, I didn't get any bonus in my rating. Such thing actually happened to me for three times, if I am not remembering it wrong, and each time the opponent's rating is way ahead of me. At first I thought that it was only because the matrix calculates something wrong. But now I have to wonder if there is something that I should not do, or else my rating won't increase even though I win?

Unrated game.

Hi, could you please tell me how to know if a game is rated or unrated? Thank you.