I had less pieces than my opponent but still I won

21 Qd8#

@anuj_guin
It's not the rule that only the player with more pieces wins. And that is very common.
Also, you won because White made an epic blunder to lose game from a completely dominated game.

Adding on to #3, position can also be better than pieces/points too.

Is no one going to say it?
Ok I will.
It's 'fewer pieces' not 'less pieces'.

You're welcome.

Say fewer material. People might be confused and think you had a material advantage but still had less pieces. Take if you had a queen but the other person had a bishop and a pawn, for example.

white had actually won he became greedy for pieces

If the oppenent had done 21 RF7 he would have won the game

ya rf7 or qd8 was mate

but he/she not played that so it's an easy win for me