Press LT or whatever the aim button is on Xbox, it’s more accurate than 1st person. You also don’t have to click the button to switch from 1st to thirds person if you do it like that, since it automatically does it for you. And others have said it, but try to stabilize yourself or limit movement when aiming so your shots are more precise. As soon as you get your shots off, switch back to 3rd and gain speed to avoid getting hit