Question

1. as busy as a bee - very busy.
2. big fish in a small pond - an important person in a small place.
3. have bigger fish to fry - to have other more important things to do.
4. fish out of water - meaning someone feels out of place.
5. shooting fish in a barrel - something that is very easy to do or effortless.
6. fish for something - to try to get information from someone.
7. a woman needs a man like a fish needs a bicycle(slogan) - a feminist slogan, suggesting that men are superfluous to women's needs.
8. teach fish to swim(proverb)- tell someone something which he/she has already known.
9. as strong as a horse - very strong.
10. beat a dead horse - to continue fighting a battle that has been won.
11. horse trade - to bargain in a hard and skillful way.
12. as weak as a kitten - weak, sickly.
13. a fraidy-cat - someone who is easily frightened.
14. play cat and mouse - to tease or fool someone.
15. rain cats and dogs - to rain very hard.
16. as poor as a church mouse - very poor.
17. buy a pig in a poke - to buy something without seeing it.
18. in a pig's eye - unlikely.
19. make an ass of yourself - if you behave so stupidly that you appear ridiculous, you make an ass of yourself. 
20. bee's knees - to say that someone/something is the bee's knees means that you think they are exceptionally good.