But babies take years of input to start speaking! I don’t want to wait for so long. As adults we can do things that children can’t and we should take advantage of that!

Even with only input, adults make faster progress than children per each hour of exposure to the language. Besides learning the language, children also need to learn about the actual world. If you get enough input every day, in 3 years you will be much better at communicating in the language than a 3 year old. Even when using comprehensible input, there are also quite a few things that you as an adult can do to speed up your learning. You can choose understandable content that are interesting and will grab your attention. You can even listen to more hours per day than many babies. If you are thinking of studying grammar or vocabulary as a way to speed up your learning, we explain the reasons why that doesn’t work in this question: Isn’t it a lot faster to study common vocabulary and grammar?.