Типа того:
He understands me
Does he understand me?
He doesn't understand me
He doesn't understand me? - это не совсем вопрос, просто переспрашиваем, подразумевая [Do you mean] he doesn't understand me? (а вот вопросы: He doesn't understand me, does he? = Он ведь не понимает меня? ; Doesn't he understand me? - Неужели он не понимает меня? )
И аналогично:
She loves you
Does she love you?
She doesn't love you
She doesn't love you? (She doesn't love you, does she?; Doesn't she love you?)
В последнем случае важно понять, какого рода вопрос вы хотите задать.