To begin with congratulations to the author for such an interesting start, and for planting such a "unique" mc construction.
Now having so few chapters makes it hard to judge a story at first, so many times what starts out as something spectacular turns to crap.
So in this review I will try from my experience as a reader of a lot of Harry Potter stories to give some parameters of what in my opinion differentiates a mediocre story from a good one.
First is the beginning of a "villain" story, which is something that is rarely handled well, usually due to a lack of resistance to criticism from the authors. My advice if you are going to make a Grindelwald type character is not to do it half-heartedly, he has to be charismatic, manipulative, with a superiority complex, a bit detached from emotions and cruel. All of these characteristics have to be realistic and consistent, they can't be changed abruptly on a whim since the mc already had those characteristics at a young age.
The second recommendation is to keep in mind that neither children are too smart nor adults are too dumb so the characters must be realistic, all adults cannot be easily manipulated nor can all children be naive, in other words use nuances.
Third tip, and in my opinion what makes a story turn to shit. The world building should be "realistic" following the parameters Rowling builds in the Harry Potter world and innovating within them, in other words, no multi-verse travel, no talking dragons, or mystical powers of the founders, no Chinese novel type cultivation, no magical core, no accelerated growth, no mc being able to command adults as a child or teenager no matter how powerful he is (beware that this is a very common mistake), or that he is more powerful than Dumbledore in his first 5 or 6 years, etc.
The important thing in my opinion is to plan the story well and have coherence with the world you are trying to raise, for example, Grindelwald is very hated by most in the magical world especially in the continent so being related to him is very dangerous so going to Hogwarts in a magical country where much of the high society is xenophobic and society is closed, besides being a breeding ground for young followers (as Voldemort did before he became a moron) is the right explanation why not to go to Dumstrang, a place where grandchildren of people killed by Grindelwald go.
The last tip is don't rush the story, it has potential, many people will not like it and they are very vocal about it, but I assure you that many people like me like a cruel story, the one of a real villain, don't soften it to the (Mc). I also hope you don't concentrate on making the mc op give him time, he can be a genius but in life everything is time, no one can study 24 hours a day.
This type of character should use politics like Tom Ridle in his time, concentrating on the young in, on the student body, adults do not follow children no matter how mature or powerful they are, is something to be proud of. Lastly don't forget Grindelwald is being hunted. Good luck with the story and to emphasize this is just my opinion and you don't have to follow it or share it.
Lastly, I don't speak English very well so I translated it, sorry if I don't understand something very well.