I am a friend from Tunisia. Well, for 'how are you' we say: chnia/ech ahwelik? if you are speaking to a person, and 'chnia ahwelkom' if you are addressing many.
"I am fine": labes, alhamdu lElleh (thanks be to God, to mean fine) or bkher..
Moreover, arabic slangs are no longer specific to its countries because media and the immigration made them used by different arabs.. the Egyptian phrase "ezzayak" (how are you) is very often used nowadays by Tunisians especially between friends or very close people (veeery informal)
As to Hesham, to some extent I don't agree with you that we can understand each other as Tunisian dialect is not easily understood by our brothers and sisters among the Arabic world unfortunately.