YOU SAID:

you did this before haven't you

INTO JAPANESE

前にもこれをやったじゃないですか

BACK INTO ENGLISH

you've done this before

INTO JAPANESE

あなたは前にこれをやったことがあります

BACK INTO ENGLISH

have you done this before

INTO JAPANESE

これを前にやったことがありますか

BACK INTO ENGLISH

have you done this before