Très bien is "very good". "Trop bien" sounds like it's too much! It could be in positive or negative way, upon the context

It's like: very good and too good

Merci..!

But in French, we often say: "c'est trop bien" to insist and say that it is really awesome ! For example, "j'ai adoré ce film, c'était trop bien!" Hope it helps :)

trop : too much / très : very simple :)