Heaven or Hell?

You know, Revan, you've asked an incredibly complex question. I thought about it for a long time before putting my thoughts together.
First of all, I myself graduated from music school with a degree in piano, but I haven't played in many years.

You're trying to understand yourself, to somehow cleanse and calm your soul. I'm 90% sure that playing an instrument will help with this.
But you need to figure out for yourself whether you can do it, whether you'll stop when the initial enthusiasm fades. I'll try to explain some things to you.
1) What do you want? If it's a sudden urge to "play that beautiful melody," there's nothing wrong with that. But be sure that in the coming months you won't be able to play something like that. And that means you won't be able to "endure" until you achieve the result. But if you're willing to enjoy small successes, to get better at using your hands, to start playing a simple piece, to be able to play it slowly but without a single mistake, then this is your path to the top.
In general, the point is that since you're self-taught, no one is controlling you, there are no "exam dates," no teacher observing your progress twice a week, etc., so you need to have your own motivation. And not a distant motivation (because you can work on one piece for several months), but a daily one. Like the feeling of your own progress.
2) The guys are right when they say that you need to work hard and persistently. Just as a painter who has been painting a picture for a long time will only see a "great" result at the end, so too will a musician, unfortunately. A musical piece is learned in parts, these parts are played separately, until you start to do well. First in a slow tempo, so to speak, working on each element. Then the learned parts are played together, and the work on the piece doesn't end here. When you're technically ready (to press the right keys), the work on your "understanding" of the music begins. How to properly convey the mood, crescendo-diminuendo, how to highlight the melody, how to lead the melody. I would say that it is at this stage that your soul begins to soar. When you consciously try to play the way you understand the music.
As for the work, just for example. When you're preparing for an exam and you can play the piece from beginning to end, you simply put 20 matches on one side of the piano. You play it once - you move the match to the other side. If you make even one mistake, even in one note, you don't move the match (be honest with yourself). And so on, until you've moved them all. And, of course, you play every day. At least an hour or two or three. Some play for 6 hours every day, and these are the most talented.
3) And the most important thing. Others may disagree with me, but still.
You want to learn to play, right? And you can only learn by playing pieces that present some technical difficulties. In 90% of cases, this is classical music, and a little bit of jazz. And when you learn to play something a little more difficult, then something easy will go well. So... an hour or two a day of practice, and then as much as you want, sit down, play whatever you dream of. Whether it's pop music or music from games. It won't happen that "I'll play some Metallica, and Beethoven can wait." :D At least, that's not the right way to do it, you won't learn anything. For example, I watched the video from the first post carefully. The melody is wonderful, no doubt, but the part for the left hand is just childish, it won't help in learning.
This leads to my very important conclusion. If you don't like classical music enough, then don't do it. I'm not saying that you have to like all the pieces, you can choose them. But in general, there's no way around it.

So... let's summarize. I don't know where you live, but here's my advice. For starters, go to a conservatory and listen to a live performance. It doesn't have to be someone famous, even a concert given by conservatory students will do. Sit down, immerse yourself, so to speak. And decide if you like it.

I. Jazz Etude, which many play in music school. I don't remember which grade. Maybe in 3-4 (out of 7).
II. Jelly Roll Morton — The Crave This is in the author's performance. I like it much more than modern variations.
III. Magnus Pålsson — Positive Force I just love this one. The guy made a great piano arrangement. And he plays well.
IV. Marasy, everyone knows him, I guess.... Damn, I just noticed that Revan also has Marasy in his first post :o :o :o

...never found any talent in anything.

You have a talent for languages, I already said. :p Don't underestimate your abilities.