it starts off very well, though the premise is obviously not new, the mc seems mature & driven, but after a few chapters the book unsurprisingly degraded, it's the usual op regressor mc with years of future knowledge doing his "best" to change the future, and I don't have any problem with that, the overall plot also written quite well, as for grammar I don't have competency to assess, but the little bits & pieces of story spices details that made me cringed hard & left me wondering if the author was a horny & hedonistic teenager, firstly the constant overly glorified mc, yes it's normal for people to admire good looking & well-off individuals, but for side characters & passerby to constantly mention how handsome & beautiful the main characters are in the exact same lines is not only really cringy, it also made the world & the inhabitants seems even less interesting than it already is, if you insist to constantly glorify mc, at least be more creative , rather than the usual copy pasted "he looks so handsome" passerby comments, use variations, like describing how people looks at him with shining eyes, or hushed voices and giggles from the girls, couples arguing, bystanders taking pictures, bad dad jokes of introducing their daughter to mc, or even hyperbole like drooling over him is ok once in a long while, there are literally plethora of these things.
And then my biggest concern, the half-assed unrealistic perfectionism, good story conclusion is understandably desired, but poorly thought unrealistic good ending is worse than well thought & realistic bad one, The examples are conclusion of Mc's uncle story, its bad, but not that bad, and then Monica's, it's among the worst sh*t I've ever read, it's poorly thought, irresponsible, and unrealistic. Both made a pattern.