For example,
There are some people in the park(幾人か(or 何人か)公園にいる).
There are many people in the park(たくさん(大勢)の人が公園にいる).
There are a few people in the park(数人が公園にいる).
There are few people in the park(公園にはほとんど人はいない).
I translated your examples as follows.
Some were surprised, many were not.(驚いた人もいたが、大半は驚かなかった。)
Few understand the value of health before they lose it.(健康を失う前にその価値を理解する人は少ない。)
A few benefited from the loss of many.(多くの人の労力から搾取し、一部の少数の人が利益を得た。)
Many belittled the few who stood out.(多くの人が稀な傑出した人達を見くびった。)
I learned that "a few" means 少しはある and "few" means 少ししかない, ほとんどない.