Answer:
My opinion is that it will end pretty badly
Explanation: he will eventually have to tell her the truth. he would just have to tell more lies to keep it up. Which will eventually lead to her hating him, unless he will to learn like everything about French in the span of a few days which seems quite impractical. The story can go both ways, Joyous an forgiving, or forlorn and crestfallen, but that's just my opinion lol