Unity Game // Already created. Needs a few things. -- 2

I have already created a game. I will send you the files in private. It's very basic FPS game. You need to add to an existing game: 1- Create enemies onto the stage which can hurt player. When player's HP falls to zero, "Game Over" screen is displayed. Then the player can start over. 2- Player can fight back and kill the mobs on the stage 3- Enemies are wandering in the random manner 4- Meeting certain criteria (killing all monsters, reaching an end point) results in clearing the stage and starting over with higher difficulty level Visual & sound: 1- at least 2 custom-made materials with normalmapping 2- at least 1 personally configured particle system 3- music is playing in the background. User can mute the music 4- when monster dies, a dying animation and sound is played 5- there are controls indicating player and enemy HP