YOU SAID:
You are a girl you will date me, you will be my girlfriend
INTO JAPANESE
あなたは私とデートする女の子です、あなたは私のガールフレンドになります
BACK INTO ENGLISH
You're the girl I date, you'll be my girlfriend
INTO JAPANESE
あなたは私がデートする女の子です、あなたは私のガールフレンドになるでしょう
BACK INTO ENGLISH
You're the girl I date, you'll be my girlfriend
That didn't even make that much sense in English.