YOU SAID:
have you seen what they all can do
INTO JAPANESE
彼ら全員ができることを見たことがありますか
BACK INTO ENGLISH
Have you ever seen what they all can do?
INTO JAPANESE
あなたは彼ら全員ができることを見たことがありますか?
BACK INTO ENGLISH
Have you ever seen what they all can do?
That didn't even make that much sense in English.