YOU SAID:
Hi Jean-Jacques, how old are you ?
INTO JAPANESE
こんにちは、Jean-Jacques、何歳ですか?
BACK INTO ENGLISH
Hi, Jean-Jacques, how old are you?
INTO JAPANESE
こんにちは、Jean-Jacques、あなたは何歳ですか?
BACK INTO ENGLISH
Hi, Jean-Jacques, how old are you?
That didn't even make that much sense in English.