You have been studying English for a long time. You have a good knowledge of English grammar and you know lots of words. You can read things in English and you can communicate well in writing. You have trouble understanding what people are saying, however, and it’s impossible for you to watch English movies or TV shows without subtitles. Does that describe you?
You are not alone. Listening is usually the slowest skill to improve. For most language learners, listening is their weakest skill. There are two reasons for this:
You may be pronouncing a word incorrectly, and therefore you can’t understand the word when it’s pronounced correctly.
You are listening for the wrong words and sounds. Natural spoken English is a mixture of stressed & unstressed words, linked words, contracted words, and reduced words. Many words are not fully pronounced.