英語について。

次の英語の添削をお願いできないでしょうか？教えていただけると幸いです。
https://oshiete.goo.ne.jp/qa/10270186.html

No.1 回答者： hitumabusi2017 回答日時： 2018/02/09 00:46

1. Autumns in Japan are as beautiful as springs in Japan.

より自然な文章。
In Japan, falls are as beautiful as springs.

2. Shinano River is longer than any other river in Japan.

3. Chiba is the best swimmer in the class.

4. China roughly 25 times the size of Japan, and their population is about 10 times more than that in Japan.

5. I walked as fast as I could, but was unable to keep up with anybody.