Chess Mentor makes you better at chess.

I did Chess Mentor ,and in a few weeks I beat both my grandpas,one of my grandpas I beat twice ,and the other, 3 times

That's what it's suppose to do. But will it help you against real opponents who are more experienced than you?

Any tool (Mentor) followed with discipline is going to make you better, period. How quickly this tool helps you improve, make fewer and far more subtle mistakes and your natural talent varies from person to person.

The quality of your typical "in game" mistakes defines how well you play against stronger opposition.  If you typically drop pawns, you are not going to consistently beat an average player on chess.com, let alone an expert or Master.