
Ron G. answered 06/26/19
Multiple levels Math, Science, Writing
I love movies. But because they have to cover a certain length in a fixed amount of time, there is a chance that speakers will move quickly and their speech will seem to run together.
Then there is the issue of informal language, including casual address and colloquialisms - among Americans there are almost as many varieties of colloquial language as there are national backgrounds of speakers. We learn most of our speech at first at home, and speak like our parents, siblings and other close relations. That tends to be pretty far off from the more formal speech and writing we are taught in school.
And movies are very informal. Lots of neighborhood-related idioms and speech among friends, which especially may have crude language.
Then, movies might also be full of technical language (such as in sci-fi) or professional jargon (especially in films featuring police, lawyers, and professions that work with money).
If you want less of that sort of thing, you may want to concentrate on films made in the 40s, 50s and 60s. The language in those films was a little more formal, and the speech a little slower, than much of what we see today.
Or, on the other hand, immerse yourself in modern films and learn the parts of informal or technical English you didn't get to use often in school. If you do that, try when possible to get the book the film was made from and use it as a companion to your viewing.