How to make a turret?

I wanted to make a turret that you can sit on and shoot from manually. also (but I'm not sure if this is possible and therefore not necessary) when you are sitting at the turret, you should make an overlay and hide the turret itself for the player. also the turret should turn behind the player. Turret is stationary. https://youtu.be/gCmUqq0ujP0 - about what i want