겠다 can be translated as  I think,  I bet,  I guess, It/this looks, It must be.

겠다 can be used to express a wish or desire 

나는 지금 자러 가겠어. I'm going to go sleep now. 내일은 꼭 그 일을 끝내겠어요. Tomorrow I'll definitely finish the job.

짱증나 죽겠어.  I’m so annoyed that I could die. 힘들어 죽겠어. So tired that I’m about to die.

꿈이었으면 좋겠어요.  I wish I was dreaming. 술 끊었으면 좋겠어요.  I wish I would quit smoking. 

열심히 하겠어요.  I will work hard. 금방 하겠어요?  Can you do it soon?