有几句英文俚语怎么翻译?

问题描述:

有几句英文俚语怎么翻译?
fly on the wall:
Shut up! I think there is a fly on the wall.
kill an elephant:
He asked you to adjust the carburetor, not rebuild the motor. Don't kill an elephant.

fly on the wall:未被察觉的观察者
Shut up!I think there is a fly on the wall.
别说话!好象有人在偷听.
kill an elephant:费力气做(不必要的)事
He asked you to adjust the carburetor,not rebuild the motor.Don't kill an elephant.
他让你调调化油器,又没让你改装发动机.别白费力气.