"אבא, מה קורה?"
Translation:Dad, how are you?
In Hebrew you would usually ask "Dad, is everything OK?": אבא, הכול בסדר? If you are asking about feelings, health, etc.
If you want to ask about something your dad is looking at, for example if you cook for him and he makes a face, you can use the more direct translation: אבא, מה לא בסדר?
Correct. Actually not necessarily close, but someone you want to be very informal with, e.g. if you're a teenager addressing another teenager. OTOH I doubt if I'll ask my father this (I'm 45 years old), and if I would it would be half joke ("look, I'm talking to you like a teenager"). I haven't seen this level of informality so far in the lessons. In fact I'm not sure it's a good idea to teach it in a beginners' course; as informal as we Israelis are known to be, in many contexts, using it might come out a bit awkward.
Actually הכול: https://hebrew-academy.org.il/2018/06/10/%D7%9B%D7%9C-%D7%90%D7%95-%D7%9B%D7%95%D7%9C/ though I think most Israelis tend to spell it without the vav.