YOU SAID:

if only i had known this big dummy would do this to me

INTO JAPANESE

この大きなダミーが私にこれをすることがわかっていれば

BACK INTO ENGLISH

If you know that this big dummy will do this

INTO JAPANESE

この大きなダミーがこれを行うことがわかっている場合

BACK INTO ENGLISH

If you know that this big dummy will do this