YOU SAID:
you've done this before havent you
INTO JAPANESE
あなたはあなたがいない前にこれをしました
BACK INTO ENGLISH
You did this before you weren't
INTO JAPANESE
あなたはそうでない前にこれをしました
BACK INTO ENGLISH
You did this before you didn't
INTO JAPANESE
あなたがしなかった前にあなたはこれをしました
BACK INTO ENGLISH
You did this before you didn't
You've done this before, haven't you.