naive

It was naive of him to believe that he could get rich overnight with that scheme.

(Chinese) 他竟然相信靠那个方案就能一夜暴富，真是太天真了。

Her naive attitude toward politics changed after she started working at the capital.

(Chinese) 在开始在首都工作后，她对政治的幼稚态度发生了改变。