In English, native speakers use a lot of idiomatic phrases everyday. These idioms can be proverbs, informal phrases or common phrases.
If you want to speak English, or you want to learn English you should spend sometime to learn idioms or to learn about idioms because they are very important in your English learning.
If you study formal English, I mean English grammar and formal phrases, and after that you go to the US maybe you cannot understand one phrase.
To learn this type of idiomatic phrases in English you should be a good listener, you should spend all your time listening to English. You should listen to one English idiom more than 40 times to have it in your brain.
You can't find English idioms if you study grammar or if you study English at schools.
The only way to learn English idioms is to listen to native speakers and whenever you hear a phrase that is not understandable (and you understand each word individually) you open your book and you see the meaning. When you hear this same phrase another time, you may understand it, and then you will learn to use this idiom.
Learning English idioms takes a lot of time because there are thousands or millions.
You will never learn all English idioms, but you should know at least 500 American expressions, the most used ones.
Don't open your book to look for idioms and to learn them, open it only when you hear a weired expression
And now I will give you an example of English idioms, an American expression that is used a lot by native speakers:
Above and beyond: it means more than is required
Let's put it in phrase: His efforts were above and beyond! It means that he had done all what he had to do, AND he has also done an additional work.
If you don't have a book of English idioms, or you don't know which book to choose, I advice you to don't waste your time looking for English idioms books because I just selected some ones for you: