I can't help you with stuff relating to your novel's genre, as I've never really written anything in that sort of genre, but I can give you some general writing advice and things you could improve. Keep in mind that I'm not exactly an expert, so take everything with a grain of salt.
Tenses are important, and easy to accidentally slip up in. Pick a tense and stick with it. You seem to be writing mostly in past tense, but here and there you have sentences in present tense.
Conversations. Although you sometimes do, you tend not to specify who is saying what, instead implicitly alternating the person speaking. This way is fine - if, and only if, there are only two people in the conversation. Once a third or fourth person enters the conversation, it'll become really difficult for a reader to keep track of who's saying what. I find personally, although I couldn't speak for other people, that it's much easier to follow if you put a simple "xxx said" at the start or end of the sentence. You can also use this to give extra meaning or inflection to what is being said. I use
this list fairly often.
Repetition. I find that it sounds/looks much better if I avoid repeating words or phrases too often, particularly at the start of paragraphs. For instance, 'I missed you so much. I have a lot to tell you" I hugged her so tight.' Now, I'm not saying that it's some cardinal sin to repeat the starts of sentences/paragraphs - two in a row is not so bad, so long as it's not happening all the time. Above that, though (say three or four in a row), I shy away from doing unless I really have to. The example before I would recommend changing to something along the lines of, 'I missed you so much. I have a lot to tell you." Wrapping my arms around her, I hugged her tightly.' Strictly speaking it isn't much different, but it has a bit of a break in the middle of the repeating 'I's.
Repetition also ties into what I was mentioning about conversations. If every line in a conversation was to start with 'xxx said' or 'yyy said'? Not great. Try to switch it up between starting and ending with that, even putting it in the middle sometimes, e.g.
"This is some sample conversation." He said. "Nothing interesting here."
And don't just cycle between the three options, just use what feels best for each particular line or whatnot.
In terms of spelling, I didn't notice any problems. Grammar is pretty good too, just the occasional missed full stop - or in one case, an extra full stop. I also notice that you don't use commas very often, generally using lots of short sentences. There's nothing wrong with short sentences, but you want paragraphs to feel natural, to flow. In terms of speaking, a full stop is just that, a pause in speech, an end of the line. For example, this is how this paragraph will be read:
'I need to sort out everything [PAUSE] One thing for sure [PAUSE] As of this day, I'm 17 [PAUSE] Studying in St. Jeanne's School of Magic [PAUSE] Although it is entitled as school for magic, the school also have a system called 'The Knights' [PAUSE] Just like the system is called they taught students swordsmanship and magic [PAUSE] They apply magic to their swords unlike mages who use wands or staff or gems [PAUSE] Almost all the students under this system are guys [PAUSE] If you are talented enough and graduated in a university with a high distinction then you can gain advantage and title all to yourself and help the family name [PAUSE]'
It makes it sound like she has to stop and think to remember each detail individually, rather than as a cohesive whole. Basically, it makes it seem like she's slow. Mentally. Still, I'm not saying you should use as few full stops as possible or anything like that - that would make it seem like the character was extremely talkative and flits between topics like a verbal train rapidly switching tracks. If the character
is actually like that, then there's no problem. But it's something to be aware of.
On another note, the whole part in your chapter where she's in the back garden thinking about things, I could understand none of that because it says at the start of that bit that she's thinking about the present, and it's all in present tense... It mentions that she is married to this person, but five minutes later she's asked if she's agreed to go out with him? Was she thinking about the past life after all? But in the middle she's thinking about school and advanced technology so it makes me think she's thinking of the present? That whole part confuses me massively.