You did learn how to sharpen it?
He removed the blade and proceeded to talk us through how to properly sharpen a blade, how important it was to balance it, then properly torque it to the motor shaft. As his wife left with the mower he remarked that most people just didn't have a clue about how to sharpen a blade.
Couple minutes his wife came back and said it was worse than before, he had put the blade on backwards.
He knew how to sharpen the blade and was so impressed by having an audience, he proceeded to get careless and installed in one of the two ways it would go on.
They need to make things that only go on one way for those who have limited ability to focus on the task at hand and for all the rest of us who will find the alternate incorrect installation method more appealing.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)