You can say: "That's a bit personal, I'd rather not talk about it." "In my culture we don't discuss those things with strangers/colleagues." "I don't feel comfortable answering these questions." "I'd prefer not to answer."

I agree with Bill. You can answer what you would say for a question you do feel comfortable answering. "Where do you live?" "I grew up in Chicago." (Not the answer to the question that was being asked, but most people won't push, and if they do, you can fall back on an honest, "I don't feel comfortable answering that.") This is very common, especially if you're doing Public Relations work.

well it's up to u , u could just do not answer him/her

This is going along the same lines as the previous answers, but a little farther, which might be appropriate in some cases. If you want to step the person back completely from your private life you could address the person from the point of view of citizen to citizen. You could address him as "Citizen", and turn the conversation back towards what is appropriate between citizens, which does not include the personal. In most cases that you would run out of appropriate conversation matters pretty quickly. I think the French were doing this for awhile after their revolution. I'm not sure it worked very well for them, but its worth a try.

Easy question , just tell him/her that you are busy in some work