[Coder-san]

If you're calling the polygonal edges on the car selection to be precise then you are still in the learning stage my friend, regardless of your disclaimer that you did in a hurry.
You cannot precisely select with a pen tool, at least not as fast which is the whole point of using Photoshop in the first place.
You have to use different tools for different raster images. In this image you posted best would be to blend.