What that mean : Wanna catch me up?

It is usually a variation on the phrasal verb "to catch someone up" meaning to be informed of all the things that have transpired recently such that you have the same knowledge of what is occurring as the other person. So "Wanna catch me up?" means, in other words, "Would you like to tell me what has been happening?"

Another phrase you may hear with a similar meaning is "Can you bring me up to speed on what has been happening?" There are lots of ways of saying it.