The flow of English involves connecting words together in thought units, which can be difficult for the brain to understand if you're used to reading the language. It's important to learn how to listen and not just hear, by focusing on what matters and filtering out unnecessary information. To improve understanding of fast speech, expose yourself to spoken English through audiobooks, podcasts, movies, and TV shows. Listen to different speakers with different dialects to become more familiar with various accents. Practicing your own pronunciation and learning prosody will also enhance listening skills, particularly by understanding how words are grouped, connected, and reduced. By developing these skills, you can become a better communicator and understand fast English more effectively.