I make Sniper FPS game and Android build it but it slow how i fix it

i make a Sniper Fps game.The enemy are coming towards sniper(Player) is shoots the enemy. and increase the score.
problem is that when i build it . it will running slow on device while moving around the camera while shoot enemy

12.jpg is right part of the Scene blue circle Shows the player arrows shows Enemy comes directions
13.jpg is left part of the scene.

anyone Give me suggestion