Yes, "I'm fine, thanks, and you?" is typical classroom language. It doesn't sound very natural, though. Responses vary a lot. "Fine, and you?" or simply "I'm good" are very common.

The answer to this depends on the type of relations you have with the person who is asking. In a formal setting you normally wouldn't hear "What's up" unless the person asking is actually trying to make the situation feel less formal and stuffy. If you want to be still somewhat formal and polite about it you can say something like "Oh, nothing much, and how are things with you?". Also, in formal settings the answer you have learned in class is perfectly suitable. In more casual settings or among friends or with people who have known each other for some time, you can say things like: -"All is well, thanks! What about you?" - generic friendly response -"I'm great and happy to see you. And how have you been?" - if you are in a good mood and haven't seen the person for some time. If you are talking to a close friend, you can be more specific and go into more detail both in your answer and in the reciprocal question, for example: -"I am mostly well, but tired. What about you? Is your boss letting you go home earlier these days?" - you'd be giving a more honest answer about yourself and asking about a specific issue you know your friend has been having a problem with. If somebody asks "What's up" in a casual setting, you can either be neutral about it ans something like "Same old, you know. How about you?" Or with a friend, you can actually answer with specifics: "I've been pulling all-nighters studying for the exams.

There are a bunch of ways to answer questions like "How are you?" but here are some general ones I hear and use often: "Oh I'm good, what about you?" "I'm fine, thanks. How are you doing?". The word "doing" is optional but I hear that a lot of people use it, well at least where I live. That's all I can think of right now, hope this helps.

It depends on how you really are doing :) If you are doing well you can possibly say: "I'm doing great!" or "Fantastic!" If someone asks What's up you can say "Nothing much, you?" It means you're doing well and things are still same as always. If you want another way to ask how someone else is doing you can ask "How are things?" or "You doing well?" Hope that helps a bit!!

If someone asks you "How are you?"-you can answer in many different ways: Great! Terrific! Awesome! Pretty good! Okay! If they ask you, "what's up?"-you can answer Not much, you? Busy day! Great day! Just doing this or that (fill in what you are doing) I hope that helps-those are just general ideas!