Isn't there something better you should be doing?
你没有别的事要去做的么？
Who are you to tell us what we should be doing?
你是什么人，可以要求我们做这做那？
They feel they should be doing something useful with their time.
他们感到应该用他们的时间做些有用的事情。
You know what we should be doing.
你知道我们该干嘛吗。
I just feel like there are more important things I should be doing.
我觉得有更重要的事该做。