[lch]

True, the first thing that you'll learn when learning a second language is the vocabulary. That's to give you access to the objects you'll have to interact with. But it's only the first step. To really understand a language, you have to learn its grammar. That's what will make the step towards being able to steer constructing your sentences with the words falling into place and connecting automatically while you make up the sentence, without the cerebral effort of fishing for the "right words" and going through a map native->second language all the time. You'll switch your language mode like pulling a trigger in your brain.

It's the same as children are taught and learning to speak.