There is no "correct" answer, but there are a few things you can say: Q: How have you been? A: I've been doing great! A: I have been well, thanks. A: I have been good, thanks. A: I've been a bit sick. A: I haven't been that good lately. A: It's been tough. A: I've been terrible. A: Not that good. It depends on how you want to reply. "How have you been" Is usually asking what you have been like since you last saw the person, or spoke, or etc. For example if you last saw the person when you were happy, but you are now sad, you would say: Q: How have you been? A: Not so good lately. Or in reverse (if you were sad, but now happy) Q: How have you been? A: I've been doing better lately. There are many things you can say in response, it depends on your feeling, there is no "right" answer :)

It is almost the same as "How are you?", but referring to the period of time. Possible answers - "Good", "Fine", "Excellent", "Great", "Not bad", "Normal"- positive; "Not good", "Bad", "Awful" - negative.

I think there is a bunch of ways to answer on that question. We can say there is no correct answer to that, but I had that problem when I was preparing for the Cambridge speaking test, not long ago I found this Blog article, and maybe it will be useful for you to read this article https://www.krisamerikos.com/blog/how-have-you-been-learn-what-does-this-question-mean-with-answers

For your help I would answer with the same verb tense...I have been OK. "How are you?" "I'm Ok!" "How have you been?" "I've been Ok!" Hope that helps you dude :)