It is PURE GREETING RITUAL and the answer is ALWAYS
"I'm fine, thank you, how are you?"
There are very small variations in the actual wording, but basically that's it. Memorize it and say it.
Any actual COMMUNICATION, about health or anything else, comes LATER in the conversation.
If you are actually sick, e.g. you are in the hospital and someone came in to visit, it might be a little different, but even then it would be something like it.
"Hi, XYZ, how are you?"
"I'm fine now that you're here. Oh, what lovely flowers, thank you!"
"No, really, XYZ, how ARE you? You look pale. Should I call the nurse?"
"Well, I just got out of surgery yesterday and it still hurts when I cough, but it's better than it was. I'm doing OK. Maybe if you could hand me that glass of water?"