improve和upgrade词义不一样。

improve vt. 改善，增进；提高……的价值

vi. 增加；变得更好（应用范围更广）

upgrade v. 使（计算机、软件等）升级；改善（尤指服务）；给（飞机乘客或宾馆客人）升级；给（某人）升职；提高（某事物的）地位

Improve是提高，改进，而 upgrade是升级。例如

There is so many thing needed to be improved for our country, transportation systems needed to be upgraded, roads needed to be improved and upgraded as well, internet neede to be improved and upgraded to face 21st century.