she will be an actress( )two years

she will be an actress( )two years .
为什么用in而不用after?
he said he found learning chinese( )because he couldn't understand people
为什么用frustrating而不用frustrated
(1介词IN 加时间段表示将来； AFTER 加时间点表示将来,加时间段表示过去
（2）FRUSTATING 用来修饰事物,FRUSTRATED 用来修饰人的,
frustrating 形容词 adj.
1.产生挫折的；使人沮丧的,令人泄气的,令人懊恼的
I found the delays intensely frustrating.
我觉得这些延误极其令人沮丧.
It was a demeaning and ultimately frustrating experience.
那是一次有失颜面并且令人沮丧至极的经历.
frustrated 形容词 adj.
1.产生挫折的；使人沮丧的,令人泄气的,令人懊恼的
I found the delays intensely frustrating.
我觉得这些延误极其令人沮丧.
It was a demeaning and ultimately frustrating experience.
那是一次有失颜面并且令人沮丧至极的经历.
再问： 这里的frustrating 修饰的不就是he这个人吗？FRUSTRATED 用来修饰人的，
再答： frustrating 充当 Chinese 宾语补足语 Someone finds Chinese ( frustrating )=某人发现汉语是令人沮丧的，令人懊恼的 Someone finds Chinese frustrating = Someone finds that Chinese is frustrating 希望这次能理解明白并及时采纳，谢谢！