Hi John, I have not really heard that expression. However, sometimes I have said to a friend, "Oh, you are very witty today!" Which means that what they said was very clever and humorous. Something a little different than a normal response. One could say, "You are full of wit and humor today," but it is rather uncommon, at least to me. The thesaurus shows mischievous, playful, prankish as similar meanings. Hope this helps!:-)

Full of wit and humour is clear though it's not a common collocation. I often hear "he is the life and soul of the party."

Could you help me explain "be full of wit and humour" please?

Hopefully a native Chinese speaker will be able to answer. But - since your English seems fine, if you explained a little more, then those of us without enough Chinese skills to know the meaning might be able to suggest an appropriate phrase based on your description. I suspect your meaning might translate well to the Australian phrase 'a wag'.