Blacks 5....Ng4 is a complete waste of time. One might consider a simple move of d4 as you are going to gain 2 tempos with the blacks early knight move.Opening the game up should be to your advantage. Keeping it closed helps black more to survive. In the game , black simply hung a piece early because they failed to play sound opening moves.As always you do get and keep preasure when the game opens up.