In order to understand any language, one must know what the idioms in that language mean.  Idioms appear in every language.  American English seems to have thousands of idioms, phrases, saying and expressions.  They are often very confusing because the meaning of the group of words taken together has little to do with the meaning of the each individual word.  If you try to translate the meaning of an idiom word by word, you will be puzzeled.  You have to know the hidden meaning of the expression.  The idioms come from many different sources: some come from different countries and cultures, some go back in time to the ancient Greeks and Romans, some come from Native-American customs and African American speech.  Some of the expressions are very recent. You will find that some of the expressions you can translate and relate to your culture and language, others are completely new to you.  So, here is a short collection of different websites that offer a good range of American English idioms and slang.  Some of the sites offer quizzes and explanations as well as examples of usage. 
Please note: This Web site contains links to Third Party Sites:  The links in these various areas will let you leave the school district Web site.  The linked sites are not under the control of the district and the district is not responsible for the contents of any linked site or any link contained in a link site, or any changes made to such sites.