Writing Quality: Below Average
Story Development: Below Average
Character Design: Below Average
World Background: Below Average
Stability of Updates: Above Average* --- I suggest uploading one chapter a day so that you have less of a period where there are no updates. I noticed you updated several in one day. Perhaps this was for the contest that I'm guessing this story was for(?), but I'm pretty sure you met the qualifying criteria. So there's no reason to upload 8 chapters all on Feb 11 but have no more updates up to now, Feb 20th. This is an updating recommendation in order to cater to how readers like to read on this site. They like consistency.
Prologue---
"A girl ran behind a boy with a big bag of cookies." This isn't the best way to start a story as it's not gripping enough. It's too simple and mundane, not a great hook. Instead, I'd combine the two scenes into one. The boy and the girl have to separate (the second scene), and the boy thinks back to the previous scene when she had fallen and he piggybacked her. He thinks about how he loves her, but that fate had its way of separating them. These thoughts of him are better suited for this second scene because it's more conducive in this context and swiftly gets to the conflict of their separation.
Additionally, I caution with love at first sight for very young kids. Even if he's mature, at 7 years old, I don't believe a child has that clear and strong of the concept of romantic love. You can still keep "love at first sight" but depict it in a child's point of view that's very innocent and naive, like the fondness for a dear playmate.
"She tripped off with her tiny legs letting the mother earth to eat her favourite cookies." Turn this into: "She tripped over her tiny legs, causing her favourite cookies to tumble to the ground." Saying Mother Earth is a little awkward for this simple falling context, so I don't recommend including it for this sentence. Besides that, I can clearly tell that English either isn't your first language, or you're still learning grammar and punctuation as these kinds of sentences are prevalent in your writing.
Overall, this first prologue is definitely rough around the edges. In fact, I'd cut parts of it and incorporate the important act of separation as a flashback thought/reflection either in chapter one or later. I don't believe you particularly need this short prologue. Just jump right into the story.
The actual first chapter is much more interesting and serves as a better starter than the prologue. It gives enough mystery (she's reincarnated? what body is she in now? what happened to her in the past) and action (she's being strangled) to intrigue the reader enough to continue reading. Onto the next scene, cool, she has her own high-tech lair, that's a little different, nice. Now the questions are answered to the reader about what happened to her old body and how her new body fits into this new timeline. The fact that her cousins recognized her and knew she's reincarnated at the start of the story is an interesting twist to the usual trope. Instead of the FL being the solo revenge act, she starts with two helpers.
Continuing onto the proceeding chapters, she wants to use her husband for achieving her revenge. Your overall plot and conflict that you set up is so far good. It's what I expected from this genre story but executed in a slightly unexpected, different way. I stopped at chapter 7 because I felt that was enough to get to my overall conclusion for this story. This review is mainly for evaluating the start of your story, including how you set up the plot and introduce the characters.
Firstly, the basic plot and conflict so far is good. But the pacing feels rushed along with the romantic conflict, that's why I deemed the story "development" as below average. Mia wants to use Xian for her revenge, but she worries about falling for him because she thinks he's a typical CEO that will cheat on her and not really love her. We as the readers know this isn't true (so far based on his inner thoughts presented). I do feel like Xian is too perfect. He's good-looking, successful, loving, and understanding. Even with Mia's supposed amnesia and slip-up's in her acting, he doesn't seem to be all that suspicious. Thus, both Mia's wariness of Xian, and Xian's lovingness and consideration feels all a bit contrived/forced for the sake of the story. I suggest slowing it down a bit and add some realism to it. Make Xian more aloof and suspicious to what's exactly happening. Also, I don't understand why he was choking her before? That seems rather inconsistent with how the rest of his character was portrayed. If he's faking it though, you need to accentuate this point better. And for Mia, she doesn't need to be so aware/scared of falling in love with him, or thinking of him fondly. Technically, he's a stranger. So except for her acting, it makes more sense to think of him as a stranger before she starts developing any nagging emotions for him.
In conclusion, you have a good story idea going. But it's a little more than a skeleton at this point. I think you can flesh it out with more world and visual details, and introspective and realistic thoughts and actions of the characters. Additionally, grammar is a weak point of the story, so brush up on correct syntax and punctuation in order to make it flow better. I also recommend not using so many question marks and exclamations in narration. This makes the story feel very amateurish. Those ending punctuations ought to be for more significant and dramatic moments or questions. Instead, rework your sentences to properly end with a period. This will make your writing feel more "professional" and "serious."
Good work, and good luck!