How to make a pirate ship game?

I would start with a rigid body on your ship and begin to construct some physics code, such as moving forward, sail multipliers, etc. You are asking a pretty broad question though. A sailing ship would require discipline in a lot of areas.

this will depend a lot on how involved you want the sailing to be, do the ships have forces acting on them? how involved is the physics going to be, is there drag from the water, wind forces, does the weight of the ship make a difference to how it moves? there really is a lot to consider, if you are creating "AI" ships, you may want to explore some kind of pathfinding tutorials, and some autonomous state machine behavioural tutorials too, its a very broad subject. In my experience, you wont find someone to write a script for you here, but there is lots of advice when you have one written out, and are struggling with a particular problem. so get some basics down and build it up from there.

Ok, I will try to do something like that.