21.I take credit for Paul. 我给Paul打保票

22.there was no snap in his turtle for two years.
The "snap in his turtle" refers to sexual performance, it's kind of a "clean" way of saying a vulgar idea (also known as a euphemism). A man who has no snap in his turtle is impotent; or, unable to have an erection.
I do have an idea on how it was created. "Snap," of course, has many meanings, but most of them have to do with making a quick, sudden movement (or sound), often of a closing or biting nature. In North America, there is an animal known as a "snapping turtle," which is a type of turtle that is known to bite (or "snap") humans and other animals. From what I have heard, if one of those things bites you, it hurts a lot. Now, if one of these turtles can't snap, then there's not so much to fear--if they can't bite you, they can't hurt you. A snapping turtle with no (abilty to) snap, then, is powerless, and from there the slang was created. The word "impotent," aside from its sexual definition, also means "without power."
In the case of "Friends," they decided to use the word "turtle" in this way, and so a turtle without "snap" is understood by Franny and Monica to mean a man without (sexual) power or capability.

23.Stop cleansing my aura
aura ：a distinctive atmosphere surrounding a given source, ex: <the place had an aura of mystery>
当时的场景是Ross进来跟大家诉说他的不幸婚姻，倒了霉运的他周身象是鬼神附身一般。Phoebe 这人第一喜欢帮助人，第二她总是神叨叨的，大家还记得有一集里她看到一只猫，就说是她死去的妈吗？于是Phoebe想帮Ross把霉运赶走，PhD Ross自然是反对封建迷信的，就对Phoebe说，意思是你别烦我了，省省吧。

24.brackety thing,whim guy,worm guy
bracket thing是组装家具的支架之类的东西
whim是一种类似起锚器或绞盘的东西，用于把比较重的物品提起来
worm guy是指代螺丝钉，因为螺丝钉上的纹路与worm很相似

25.Rachel说度蜜月到Aruba,为什么Ross提到 Big lizards
当Rach提到本想去Aruba时，Ross原本想说Rach不能去渡蜜月是太遗憾了，但突然意识到不应该说这些，急忙改口找些其他话题而提到Big lizards，并不是Ross对生物感兴趣。我认为到底Aruba有没有Big lizards无关紧要，只是Ross转换话题的一个借口而已

26.There's Rocky Road, and Cookie Dough, and Bing! Cherry Vanilla. You could get 'em with Jimmies, or nuts, or whipped cream!
jimmies是一种经常撒在ice cream上的巧克力味的小糖果棒。bing就是一个拟声词。

27.in bound of holy matrimony,就是结为夫妇，在神圣婚姻的约束，范围内 ．