Dear Gui_doz,
I am a certified, full-time chess coach, so I hope I can help you. 
Everybody is different, so that's why there isn't only one general way to learn. First of all, you have to discover your biggest weaknesses in the game and start working on them. The most effective way for that is analyzing your own games. Of course, if you are a beginner, you can't do it efficiently because you don't know too much about the game yet. There is a built-in engine on chess.com which can show you if a move is good or bad but the only problem is that it can't explain to you the plans, ideas behind the moves, so you won't know why it is so good or bad.
You can learn from books or Youtube channels as well, and maybe you can find a lot of useful information there but these sources are mostly general things and not personalized at all. That's why you need a good coach sooner or later if you really want to be better at chess. A good coach can help you with identifying your biggest weaknesses and explain everything, so you can leave your mistakes behind you. Of course, you won't apply everything immediately, this is a learning process (like learning languages), but if you are persistent and enthusiastic, you will achieve your goals.
In my opinion, chess has 4 main territories (openings, strategies, tactics/combinations and endgames). If you want to improve efficiently, you should improve all of these skills almost at the same time. That's what my training program is based on. My students really like it because the lessons are not boring (because we talk about more than one areas within one lesson) and they feel the improvement on the longer run. Of course, there are always ups and downs but this is completely normal in everyone's career.
I hope this is helpful for you. Good luck with your games!
I've been playing for almost 6 years now, starting when I was almost 38 and now I'm 44.
), but nobody had ever introduced me to tactics and strategies and for a long time chess was just a "boring game" I vaguely had an idea about and almost never played. The only few times I played I was easily losing because I had really no idea, not even of the basic opening principles.
) I started playing faster and faster, and now I play mostly blitz games. Occasionally I still play some daily, especially in tournaments, but I focus on the moves way less than before, sometimes even making a move within seconds only to realize immediately after confirming it that it's a blunder. 
As a child my grandfather had explained me how to move pieces (except for en passant lol
Everything changed when one of my colleagues got into chess and I got currious, especially after he mentioned the value of the pieces to explain why he had traded pieces. I had no clue pieces could have a value! I got intrigued and found some basic lessons here on or youtube and started figuring out there was some "order" and "best practices" in this mess!
The first months were exciting as I was learning the opening principles, some common tattics, some basic openings and gambits.... but that's it, after the first year maybe I got stuck approximately at the same level, with only minor slow improvements due to experience.
When I started playing I was playing mostly daily games, and I would consider the 30 minutes format a "fast" game. I was taking a lot of thinking before every move and joining some daily tournaments. The more I got acquitted with the basic openings (my favourite being the italian game, but it is not because I'm italian
I still play more or less every day, sometimes compulsively (I mean, I find myself starting games almost without realizing, out of boredom, while I was on the computer and had nothing else to do, pretty much either I check some facebook s**t or I start a game... same kind of brainless addiction).
After the first times in which my rating was steadily climbing, I now find myself floating always around 1200-1250 in almost any time format (sometimes, playing out of boredom and being tired or distracted I do get lower ratings, but I also had better ones: my all time best scores go from 1189 in bullet to 1478 in daily).
So, is this my limit?
My brain cannot work better, or simply I cannot focus more than this?
What can I do to try and improve, provided I still have room for improvements?
PS: I'm well aware of not being a genius, but also of not being that stupid and maybe being slightly over average (I once got an IQ rating of 128 for what matters)... so I think I might still have some little growing space in terms of logic, and my main problem at the moment is lazyness: playing often the same lines, playing out of boredom, playing quick games with no much concentration relying on the few lines I know best (but often can't name as recognised openings) and/or some tactics (I have a rating of 2000-2200 in the puzzles). I've always been hyperactive by the way. Never diagnognosed ADHD but I suspect I had it as a kid, although through the years I trained myself to focus more