How does the point system work when winning? Several times I lost 1 or 2 points when winning!
Not possible.
I am assuming you are talking about game ratings. Even if you are rated 1,000 points above your opponent, you cannot lose points when winning.
Please provide a screen shot of your archive showing what you think is a reduction in your rating when you won.
I think he is talking about computer analysis. I agree that sometimes you can be winning a game and the analysis will show that you are losing by a point or two. The last game I had analyzed said something like "you blundered(1.90),..., you blundered(3.80),..., you blundered(8.19),..., Checkmate, you won.
If that's the case, think the following through.
A blunder is a move that costs you, say, >1 point in material.
You have two options, one which gives you +3.05 and one which gives you +8.91. Playing the former is a blunder by those standards.
It is not unusual where a very top chess engine will think it is winning when it is really a draw or that a very top chess engine will miss a win.
How does the point system work when winning? Several times I lost 1 or 2 points when winning!