YOU SAID:
Hey girl, what are you doing later?
INTO JAPANESE
ねえ、女の子、後で何をするの?
BACK INTO ENGLISH
Hey girl, what are you going to do later?
INTO JAPANESE
ねえ、女の子、後で何をするつもりですか?
BACK INTO ENGLISH
Hey girl, what are you going to do later?
That didn't even make that much sense in English.