The Idea
So I have a game, a ww2 game. It has ship cannons in it, I want the player to be able to control the ship cannon to aim, just like a car. For example here is a youtube video: https://youtu.be/2zgQogvKS_Q?t=245
I am asking how I could create this script, would I would need to do, and any problems that I would need help with to be solved.
I hope this explains enough.
This would be a matter of moving the whole part while obeying physics. I strongly recommend reading up on the topics of Motor6D’s, which will allow you to create rotational joints with constraints on field of movement along with Context Action Service to specifically Bind the WASD keys to moving just the Cannon when you are sitting in the Seat. Along with these, I’ve heard that Fast Casting and TweenService might just help you out. I wish you a lot of luck with this endeavor. 
I’ll try, I’m not the best scripter and this will probably be a problem but I’ll try