Take a moment to take yourself back to when you were learning English. You’ll remember that you started learning to speak by listening to your parents repeatedly speak simple phrases and eventually repeating them back as best you could. It wasn’t until much later that you actually had to learn to read, let alone study grammar.
Basically your environment enveloped you; English was all around you and slowly but surely you absorbed the language from what you heard around you. You made lots of mistakes you were expected to make mistakes but the result was that you were able to speak English without actually having to study it.