YOU SAID:
Did you added butter to your friends?
INTO JAPANESE
あなたの友人にバターを追加しましたか?
BACK INTO ENGLISH
Did you add the butter to your friend?
INTO JAPANESE
あなたはあなたの友人にバターを追加しましたか?
BACK INTO ENGLISH
Did you add the butter to your friend?
That didn't even make that much sense in English.