"green" here refers to a green "space" a park or other public area of greenery. It's a rather English sort of English, I suspect, often used in conjunction with the word "village".

"The Federal Bank surprised Wall Street big time"
My guess would be that the catch is the idiomatic nature of the phrase - "big time" simply meaning "a great deal" or "very much", with no literal connexion to time of any size.

"Empty vessels make the most sound." (I know it's an idiom, what does it mean?

People with nothing to say are the ones talking the loudest. Shakespeare's line "full of sound and fury, signifying nothing" expresses a similar idea. . If you bang on an empty vessel, it will make a lot of noise precisely because it's empty. Likwise, a person bereft of meaningful contributions to a discussion will balther on endlessly, hoping to obscure the absence of quality by the excess of quantity.