Ya I'm fine, why?

This one threw me off for the longest time, and still gets me :)

You know how back home, normal people say, 'hey, how's it going?' when they greet familiar faces? Well here, you say, 'hiya, you 'right?' (translation: hello, you alright?) and the proper response seems to be, 'ya, you?' As simple as that. My flat mates (the people who live with me on my floor) say that to me all the time whenever they see me, and it throws me off all the time. The first couple times had me clutching my face thinking 'ya I'm... fine, I think. Should I NOT be?' and making a complete fool out of myself, but now I've learned. But for all it's worth, I threw off all my flatmates by saying 'hey, how's it going?' None of them really knew how to respond to that either. Good times...