Slang is li(3) yu(3).
Here are examples of American slang. You can find other websites on slang.
Student or Learner
what is slang ?
how we can use it well ?
Just a word of caution about slang -- if this is not your native vocabulary, don't use it.
This applies to native speakers of English as well, who sound ridiculous when they try to use the slang of others groups. Parents sound silly when they try to sound like their children. People from the suburbs sound ridiculous when they try to sound like urban street youth.
English learners will sound equally ridiculous. Let slang come into your vocabulary naturally, but don't memorize it and try to insert it into your speech.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.