Although students can learn grammatical rules in a short period of time they can’t achieve fluency in speaking. There might be some reasons. Whatever the reason is, there’s always a way out. There is a golden rule, the first thing you should do is “speaking”.
If you don’t use the words, idioms, phrases which you learned through a day, you will probably forget them after a month. The speaking process sends a signal to the brain, as a result, you will be able to keep these words in memory forever. The way to learn good English is to speak it well.
“Shadow recording” will help you. In this process, you choose a video, listen to it carefully, and try to repeat the sentences, then record your voice. So, you can improve your pronunciation as well as fluency. Don’t pay much attention to the rules of grammar, structure of sentences, details, and so on.. just try to speak more and more.