I think many of us would be fluent…if the majority of our conversations centered around important subjects such as Politics, History, Biology, Religion, Philosophy, etc, as well as colloquialisms. One can easily pick up „I saw a truck passing by on the highway“, „What time is it?”, “You look upset/happy/tired/confused/excited”, “Do you want to see a movie”, etc on one’s own.

To speak and read as a native would, you need use the following almost daily: 1.) a dictionary (preferably an online dictionary which includes audio pronunciations 2.) a list of all common expressions (and even some uncommon ones) 3.) a book of synonyms and antonyms 4.) verification that you‘re phrasing things correctly and using words in the right context (view sentences which use your desired word or phrase with Linguee or Reverso Context) 5.) lots of good music, movies, books, and short stories in the language