YOU SAID:

i am sisters mean big poopy

INTO JAPANESE

私は大きな姉妹意味踏む

BACK INTO ENGLISH

I take big sister mean

INTO JAPANESE

私は姉の平均を取る

BACK INTO ENGLISH

I take my sister's average

INTO JAPANESE

私は私の妹の平均を取る

BACK INTO ENGLISH

I take my sister's average