How i can practice more with functions , or just move on and i will know more in the next sections ?

LEARN A LANGUAGE REALLY GOOD BEFORE ANYTHING ELSE. The language doesn't matter but just PICK ONE and STICK WITH IT. Before I stared to really see growth in my learning I was "only gonna learn JS" but ended up seeing Angular and taking an Angular course, then seeing React and taking a React course and so on and so on. That probably stunted my growth for about 6 months. The one nice thing is React is really just javascript so you are still learning it but if your goal is to get a job you are hurting yourself deeply.
Here are my suggested ways to better yourself with javascript

1. Finish this course it's not bad and the front end is pretty comprehensive but the backend is too quick and he doesn't go into any/much detail
2.Pick a STRICTLY javascript course. There are tons on Udemy but my personal favorite and the one that I can vouch for and really teaches you how to understand code (which will translate to any language) is watchandcode.com. Yes both the free and premium stuff. Yes the premium stuff is $40 a month but it's priceless
3.This is the number one thing my mentor pushed me to do that I saw the biggest benefit with and what the people I mentor see their biggest growth with, BUILD THINGS in a "progressively learning" way. (your first 2 or 3 builds don't have to be this way cuz of how new you are but after 2 or 3 if you aren't doing this you are doing yourself a dis service) What that means is pick a project that you are comfortable with about 80% of the project and 20% is something you aren't comfortable with and will have to research, read docs and play around with. You can change the percentages but these amounts tend to be the best for me and the people I mentor because you still have the positive feedback of knowing a lot of it while still learning something. The closer you get to 50/50 and you start to feel bad cuz you don't know anything and start cutting corners or just dropping the project all together.
4.After you have learned your language with some proficiency and built 3 or 4 projects with just the language pick a framework and continue to progressively learn while building more projects.