If somebody says to me, "How are you?", my answer is usually, "Fine, thank you, and you?"
Is it natural to say, "Very good." instead of "Fine" in usual conversation?
It's not very common to hear "very good" as an answer, but there is nothing wrong or unnatural about it. If you want to stress that you are better than just fine, you can say "very good.....".If somebody says to me, "How are you?", my answer is usually, "Fine, thank you, and you?" That's a common and good answer. (actually 'fine thanks, and you?')
Is it natural to say, "Very good." instead of "Fine" in usual conversation?