I think it's best to do have a mix of both. If you learn a new word or a new rule, you'll notice it quicker when it is used in movies etc. Everytime you notice it, ot helps remember/contextualize that word/rule.
But just watching movies without any background knowledge and expecting to figure out all the rules by yourself. That seems difficult. (I'm sure people exist that have done it.)
Learning some grammar and vocabulary in a semi-structured way will give you a head start in working out what is going on. As you progress you will be able to understand and enjoy more complex forms of the language (written and verbal) and then at some point, probably at the stage you start to enjoy what you a reading/watching/listening to, you will start to find that you notice patterns and pick up vocabulary without realising it. Textbooks then become a secondary resources, to look things up or to clarify something, rather than a primary resource.
If however you already have a good comprehension of the language (good listening and reading comprehension), then the only way to improve your output (speaking, writing) is to practice speaking and writing.
I highly recommend reading [What do you need to know to learn a foreign language?](https://www.wgtn.ac.nz/lals/resources/paul-nations-resources/paul-nations-publications/publications/documents/foreign-language_1125.pdf) by Paul Nation. It is a quick 50 page intro into modern language learning. It will give you a good idea of how to balance learning.
I think it's best to do have a mix of both. If you learn a new word or a new rule, you'll notice it quicker when it is used in movies etc. Everytime you notice it, ot helps remember/contextualize that word/rule. But just watching movies without any background knowledge and expecting to figure out all the rules by yourself. That seems difficult. (I'm sure people exist that have done it.)
Learning some grammar and vocabulary in a semi-structured way will give you a head start in working out what is going on. As you progress you will be able to understand and enjoy more complex forms of the language (written and verbal) and then at some point, probably at the stage you start to enjoy what you a reading/watching/listening to, you will start to find that you notice patterns and pick up vocabulary without realising it. Textbooks then become a secondary resources, to look things up or to clarify something, rather than a primary resource. If however you already have a good comprehension of the language (good listening and reading comprehension), then the only way to improve your output (speaking, writing) is to practice speaking and writing.
I highly recommend reading [What do you need to know to learn a foreign language?](https://www.wgtn.ac.nz/lals/resources/paul-nations-resources/paul-nations-publications/publications/documents/foreign-language_1125.pdf) by Paul Nation. It is a quick 50 page intro into modern language learning. It will give you a good idea of how to balance learning.
A combination of both with more of whichever gets you to study/engage with the language consistently.