I should study now. (Correct)

I should play out side. (Correct)​

He should study hard. (Correct)

-엔지니어는 무슨 일을 하나요?

What does  Engineers usually do? --> What does an engineer usually do?

=> Corrected: The sentence is corrected grammatically.​

-엔지니어는 보통 다리를 설계한단다.

 Engineers usually design bridges. (Correct)​

-우와! 멋져요. 나도 엔지니어가 될 거예요.

Wow! Cool. I want to be an  Engineer.

=> Corrected: The sentence is corrected grammatically.​​​​