Is this how to reply to "how is it going?"?

'Well' may be more grammatically suitable than 'good' , and 'what about you?' could be more proper as well, although both these are quite all right and acceptable, I think.

Most people don't talk like that. To answer, "It's been going pretty good," is a bit stilted. More natural would be, "Okay," or "Not too bad," or "Just fine." Any of these can be followed with "You?" or "And you?" or "And with you?" So, something like, "Okay. Thanks for asking. You?" would carry the dialogue in more natural way.