Good Start
"Firstly, I'll start with something you're probably already aware of - the grammar and spelling needs work. I would download Grammarly, the free version would help you a lot.
I think the plot is decent, but it's a trope I've seen a lot before in stories on this platform. I think it needs something to differentiate it from the rest. These plots are used a lot for a reason, becuase they work and so for that reason it is engaging, it just needs something extra to really set it apart - convince me why I should read your story instead of the other ones of this trope.
The style is fairly good, in some areas the dialogue feels a little strange and unnatural, but I think someone pointed that out in the comments already (I would definitely follow the advice Eugene has commented, it's all things I agree with 100%)
I think what you have done well is create a good character in Harry, he's very likable. Diana is likable as well, and I enjoy that she's not helpless like some female characters are made out to be - however, it is confusing when the title of the book is "Weak" and the female character doesn't reflect any of that? I would maybe workshop the title a bit (and change the cover so that it's not the same as your other book)
I also think some of the chapters could be longer, either by consolidating two chapters into one or simply adding more detail/action to each chapter. The average chapter should be about 1000-2000 words (I think that's what Inkitt recommends as well) - I get the feeling that some of these chapters fall into that range, but some of them feel very short
Overall, keep on trying - I think the first step is fixing the grammar and Grammarly would really help with that! Good lucky!"