I would advise you against playing this computer. Sometimes it makes mistakes that are too unnatural for human players (6...Nxe4?), other times it plays moves of quality very much superior to all other moves in the game. Maybe if you play humans you will have a better chance of understanding your opponent's play.
I took a quick look and I think your main problem in this game was development. For instance, you played 9.Re1. You could have played Be3 or Nc3 to bring all your pieces out. The moves 9.Re1 and 10.Bf1 did nothing to improve your position. Even after 12...Nd4 I think you could have gone for 13.Rg2 followed by the natural moves Nc3 and Be3 and white should win with the extra piece.
To improve your game I suggest you pick up some basic opening knowledge and train tactics! 
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Please Help Me.