"make a mountain out of a molehill"

means:

make something seem much more important than it really is/ to exaggerate

Example: Calm down. There's really nothing to worry about.You're making a mountain out of a molehill."

"an eager beaver"

means: somebody who is always willing to volunteer or to do extra work

Example: She is definitely an eager beaver. Any time there's work to be done, she's the first to say she'll help."

"as easy as pie"

means : something is very easy

Example:

I thought you said this was a difficult problem. It isn't. In fact, it's as easy as pie."