Do the three days exceeding seven days, after the ten days of the menstrual cycle, count as menses or not? And what should be done about that? And is there a solution to reduce the number of menstrual days?

It is not true that the maximum duration of menstruation is seven days. Rather, it is fifteen days according to the majority of scholars, and ten days according to the Hanafis. A woman is obligated to consider herself menstruating as long as she sees blood, and she is not considered to have istiḥāḍa (prolonged non-menstrual bleeding) unless the blood, and any yellowish or brownish discharge associated with it, exceeds fifteen days.