Is there a literal translation to the english language of this phrase?
This would be "Enjoy your meal", or just "Enjoy!". But you should say it before rather than after you've finished eating.
OK sorry, I asked that wrong. Is there an expression in the english language used colloquially? I don't think i've heard a lot of people say something like "good appetite" after you've finished eating
American people don't use this term, but you may say BON APPETITE to sound chic..