YOU SAID:
i dont know grandma is that you
INTO JAPANESE
私はおばあちゃんがあなたであることを知らない
BACK INTO ENGLISH
I don't know grandma is you
INTO JAPANESE
おばあちゃんがあなたなのかわかりません
BACK INTO ENGLISH
I don't know if grandma is you
INTO JAPANESE
おばあちゃんがあなたかどうかわからない
BACK INTO ENGLISH
I don't know if grandma is you
That didn't even make that much sense in English.