Why a mistake?

Hello,

first time i am seeking help here. I played this game and was wondering why 12. ... Ndf6 was such a bad move? My idea was to backup the Knight on e4, so once this one is taken (for example by the bishop), i can restore a Knight on that "good" square. What am i missing?

Thanks.

You Letting White Pushing Pawn Into c5 And Giving e5 Square For White Knight, And That Happen Later On Your Game.

Your Opponent Improve His Position And Get Active Position, As Far As I Remember As Former Nimzo Indian Player,Black Must Play c5 To Achieve Equal Position And Then Trade That c5 Pawn To d4 Pawn To Open up File For Rook on c8

okay, thanks, sounds like a good gameplan

So You Must Keep Knight On d7 To Support c5 Push For A while,You Can Move Knight Later,No Need To Hurry, In This Position I Think One Of Good Plan Is play c5 Moving Rook Into c8 Open Up c File, Play Qe7 Connecting Both Rook. And If Possible Double Up Rook On Open c File.