Ni hao ReeJay li To fully understand a movie in english like a native would take more than just learning the language academically ,that is to say by lessons and teachers, because in movies the language is used mostly will include slang , colloquial , expressions used only by natives etc ,so it would take beside the learning , mingling with natives and practicing the language with them , so you would have the opportunity to ask about new expressions ,words etc . The more you watch movies and listen to repeated expressions ,you will get hold of the language used .Lots of practicing ,reading ,listening is required too Good luck :)