"How is it going on" is not a phrase in English - whoever said this probably made a mistake. They either meant to say, "How is it going?" or "What is going on?" It's most likely that they meant, "How is it going." The first 3 answers did a perfectly good job at translating that.

The previous three answers are attempting to be helpful, but I think they are merely guesswork. The phrase in capitals doesn't really have an obvious meaning, it is plain bad English. Get a new teacher.

Does he say "How is it going?" or "How is it going ON?" Either way, it is a general question to ask "How are things in your life?" Usually, native speakers would respond with "It's going well, thanks. How are you?" Or "I'm alright, how about you?" The question is just a conversation starter. You can add more details to your answer. For example, "It's going really well! I got a job promotion/met a girl/went to a fun party last night." or "I'm alright. I had a really long day at work so I'm feeling pretty tired." Hope that helps!

"Qué te pasa", "Cómo estás"

This isn't adding anything to what the other members have said, but I just want to emphasise the fact that this sentence is INCORRECT. As Jim and Cali have already pointed out, nobody says "How is it going on?". He is probably confusing the phrases "How is it going?" and "What's going on?" - --both normal ways of greeting someone or starting a conversation. "How is it going on?" is simply bad English. Take Jim's advice and find a different teacher. A person who can't even get a basic greeting right should not be teaching English.