What would be the reply to - 'How are you'?

A reply to 'How are you?' is - I am fine. You can also say - 'fine' or ‘very well'.

Native speakers would typically say something like "I'm good, thanks. How about you?" or "Not bad, thanks. How are you?" or "I'm doing well, thanks

Ami amar bhaiyar salike biya korte chai.