For many people, learning a language involves going to classes, doing homework, taking tests and trying to memorise vocabulary. Others try to teach themselves languages using similar techniques. These are all useful things to do, but won’t necessarily give you a fluency in the language. Conscious learning of a language using these methods tends to feel like hard work.
If you really want to become highly proficient in a language, you need to spend a lot of time immersed in it. To become good at speaking the language, for example, you need to find opportunities to use it with other people, ideally in situations where you have to use it, or at least try to say as much as you can without falling back on your native language. Listening to radio programmes, watching videos, films and TV programmes, reading books and other material, and writing it as often as you can are also good things to do. This may not feel like study, especially if they involves subjects and activities you really enjoy, but you will be absorbing and acquiring a lot of the language without realizing it.
Conscious learning and sub-conscious acquisition are both good ways to learn languages. You can probably make faster progress if you study a language consciously, but sub-conscious acquisition probably gives you a deeper knowledge of it. Combining the two together is even better.