"nanu?" - you say that when you're puzzled or surprised by something, like "What is this? What does that mean?" "na gut!" - means, depending on the context, something like "it's ok";" i think you're right", "whatever..." "na ja" - an expression of uncertainty like "well...", "i'm not sure...", "are you sure?" "Alter" - is often used to adress male friends "old friend", or as an expression of excitement "Alter! war das eine tolle Party"... "von wegen" - is usually used to express disagreement "I dont think so...", "that's not right" "quatsch!" - means "nonsense" or "bulls***!" keep in mind that most of these words can have slightly different meanings, depending on context an intonation, and are widely used in colloquial spoken german.

I think that you shou learn with a native speaker ! Sorry for this .