We spend a lot of time talking about how to start learning English, how to begin from nothing, how long it takes. It is exhausting to think about.
There is light at the end of that tunnel, and it has a name: escape velocity.
A plane burns an enormous amount of fuel moving down the runway and lifting off. But once it reaches take-off speed, it passes a point of no return, and from there it flies very fast on far less fuel than the runway demanded.
What escape velocity looks like in English
When you talk to a foreign speaker, you learn automatically. You hear an unfamiliar word, you look it up or ask them what it means and how to use it, you practise using it. Then you remember it and can deploy it. That word is now yours.
When you read an English sentence you cannot make sense of even though you know every word in it, you know how to search for an explanation of the grammar and meaning, in part or in whole. You not only understand that sentence, you pick up other meanings of the words in it and the structure underneath it, so the next time you meet it, you simply understand.
Once you are moving at this speed, you have the foundation and the ability to teach yourself. Any English material you touch, any English speaker you talk to, improves you, without any class at all.
This is the destination every learner should be aiming at. Worth noting: this point does not depend on your current level, though it typically arrives somewhere after the first twenty hours of study.
The two things people past that point do well
Awareness. Knowing where you are weak and what needs work. For example, mispronouncing a lot of words because school taught you meaning and usage but never pronunciation, so the errors hardened into habit.
Control. Knowing what materials to look for and how to study them efficiently. To fix pronunciation, search "[word] pronunciation", then repeat it five to seven times until your mouth knows it, for words you have just met and words you have used for years. Keep doing that and your pronunciation steadily improves.
The better the teaching and the learning, the sooner a learner reaches escape velocity.
More awareness and control pairs
You know plenty of vocabulary and can do grammar exercises, but you freeze when speaking. The problem is you have not spoken or used it enough. The fix: talk to anybody in English and deliberately use the words you have learned. Use them often enough and they will be there when you need them.
A page of English looks overwhelming and you recognise almost nothing. The fix: change the text. Read something easier and closer to your level, and build vocabulary from there.
Spoken English sounds like noise. The fix: dictation. Write down what you hear, compare it against the script, relearn the pronunciation and repeat it aloud. Saying it correctly makes hearing it correctly much easier.