i am fine, i am okay; 난 괜찮아 [nan gwenchana] to younger or same aged 전 괜찮아요 [jeon gwenchanayo] to older or stranger or if you want to answer to 'how are you?', you can say also; 난 잘 지내 [nan jal jinae] to younger 전 잘 지내요 [jeon jal jinaeyo] to older hope it helps ; )