English essay

This is my homework of university. The topic is Japan's aging population. Also this is research paragraph.
Please edit any grammar mistakes.

To furthermore investigate the topic of the pension, this paragraph focuses on qualitative interviews. I think that the problem of pension is caused by Japan’s aging population. Therefore, to gather people’s opinions about Japan’s aging population, I asked five people this question: Could you describe the source of Japan’s aging population? Then I presented them two answers for the question: great improvement in Japans medical care or falling birth-rate. By “great improvement in Japans medical care”, I mean that compared to the previous medical care in Japan, current Japanese medical care has been developed. By “falling birth-rate”, I am referring to low birth rate of children which will promote aging population. Three people responded with great improvement in Japans medical care. They remarked that there was a disease that could not be cured before, but recently, many lives have been saved by advances in medical technology in Japan. So in other words, one of the causes of aging population in Japan, is the improved medical care in Japan which is starting to become one of the most advanced countries in medical care, Japan also has the highest life expectancy rates in the world. On the other hand, two people responded with falling birth rate. According to them, because the number of children has been decreased due to a falling birth-rate, it is impossible to balance of the number of children and the elderly. So, most people are under the illusion that aging population is progressing, because the number of elderly people is greater than the number of children. From these results, I can tell aging is caused by a variety of factors. Therefore, in order to solve the problem of aging, it is necessary to solve the fundamental problem. Furthermore, among the people I interviewed, the majority of them believe that there are the Japanese medical care system often focuses on the elderly, so it is necessary to provide the system for children as well as the elderly.