is it possible to learn a language in a few days?

Since I'm doing HTML5 I'm learning JavaScript (and later HTML) using the following tutorial https://es.javascript.info/. Since I'm not in a hurry (this is a personal project) I'm reading about 20% of the tutorial everyday, which means I'll finish it in 4-5 days.

Is that amount of time enough to learn a languje?

Plus, what is the correct way to learn a language? Go through the tutorials/books until the end and then begin to write small programs, or learning just the basics and start coding your project as you finish the tutorial later?

Usually I'd go with the latter, but this time I'm going through the whole tutorial first before beggining to code, and my mind is about to explode. JS is so different from the C/C++ I'm used to that I need to re-read the tutorial several times to understand it. JavaScript has very weak typing, and the OOP I like (coming from JAVA) is tedious and complicated in JS.