If we say somebody's a " sharp cookie" , it means smart.

如果我们说某人是“sharp cookie” ，那就意味着聪明。

This person could be a sharp cookie or someone who is not easily fooled. Very often things do not go the way we planned.

这个人可能是a sharp cookie(很难骗的人)。很多事情并不是你所预料到的。