@wewee I've read a few chapters of your novel, and I just wanted to say upfront that your synopsis is amazing. The cover looks rough but simultaneously clean, and I love it. It really made me want to read your story until I actually pulled up the first chapter and had immense difficulty understanding the sentences.
Unfortunately, grammar is a big problem among new writers here, but I can't really give any advice for that other than to get grammar-checking software and practice writing A LOT. To arrive at where I am now, I've written four novels in the past, but I can assure you that everyone starts off with tons of mistakes. Just practice, and you'll get better eventually.
Now, I want to talk about the story itself. The prologue is intriguing, but I feel that it would be much more impactful if it was told from the perspective of the undead girl. Of course, this is a personal suggestion, and I don't want you to feel obligated to write your book the way that I want, considering that I'm not the author. Honestly, I feel that the prologue can be fine the way that it is, but the synopsis was described from the perspective of the undead girl, and I feel that readers would be much more drawn into the prologue if it was also from the undead girl's POV, especially since your synopsis one your best selling points. It's really just a continuity thing,.
Following the prologue, you had a couple of chapters of people talking in a school. It's the classic mysterious/tension-filled prologue that leads into a stale beginning. It's okay to start off slow, but at least make it entertaining. It might just be the grammar messing with my head, but I feel that the newly introduced characters don't make much of an impact. I suggest introducing only a couple of key characters at a time in a memorable fashion so that the reader can really let the information sink in. Flashy entrances are always the best, but that doesn't mean that a character has to run in guns blazing.
Still, your first few chapters weren't terrible and you have a really cool concept. I think that the only thing you're missing is more practice.