YOU SAID:

well why are you late you had better be on time next time

INTO JAPANESE

じゃあなんで遅れたの？次回は時間通りに来た方がいいよ

BACK INTO ENGLISH

Well then why were you late? You should be on time next time.

INTO JAPANESE

じゃあなんで遅れたの？次回は時間通りに来てください。

BACK INTO ENGLISH

So why were you late? Please be on time next time.

INTO JAPANESE

それで、なぜ遅れたのですか？次回は時間通りに来てください。

BACK INTO ENGLISH

So why were you late? Please be on time next time.