YOU SAID:

I've done this before, didn't I?

INTO JAPANESE

私は前にこれをやったことがありますか？

BACK INTO ENGLISH

Have I done this before?

INTO JAPANESE

以前にこれをやったことがありますか？

BACK INTO ENGLISH

Have you done this before?

INTO JAPANESE

前にやったことあるの？

BACK INTO ENGLISH

Have you done this before?