There are several noteworthy elements in this piece.

1) You have a story. A real story, with a beginning, middle, third act and a conclusion. This alone puts you in rarefied company. We'll talk story structure in a minute, but your instincts are on target.

2) Your prose works. Your sentences build into paragraphs and go on to form whole scenes. Readers get really annoyed when they find that the present moment of the story gets fuzzy and ambiguous. Your narration maintains a steady movement forward, never letting us drift away from the present.

3) In addition, you handle decorative elements well. It's one thing to tell us the who, what, when, where and why of a scene. Another to do so with language that is concise, but descriptive, establishing a subjective context in which the story unfolds.

Any fourteen year old writer could point with pride at having mastered any of these elements. That you have them all under your belt suggests a firm foundation on which to build a strong body of work.

On the other hand, you're fourteen, and while your instincts and creative gifts are evident, there are some nuts and bolts details that you'll need to address.

You've chosen a first-person present POV, not one seen often. First-person, yes, and present tense, yes—both are used regularly, particularly in YA fiction. Using them both together can be a problem. One pitfall is that it's so easy to move around in the main character's head, since we're already there. The potential is great for endless introspection and internal monologue. You've avoided this with an extreme solution: you almost never leave the domain of camera and microphone, which begs the question, why this POV at all? We get to see this story through Birsha's eyes, to be sure, but we don't get to experience it through his own experiences, which are necessarily a blend of internal and external phenomena.

A bigger issue for me is the fact that you really have two different stories here, with two distinct main characters. We don't realize this until the end, of course, so that for most of the second half, we simply feel disconnected from what is happening. It's not until we discover that Birsha has ceased to be Birsha that we have an intellectual resolution. But that's never enough. Readers want to immerse themselves in your universe, and they want a payoff for their efforts. "Oh... I get it," really doesn't cut it. Part of the problem is your use of magic, which needs to be handled carefully, or it will just look like a cheat. As I say, your conclusion clarifies much, but until we get to that point, Birsha seems to have simply transformed from a nerd into a vengeful god hurling lightning bolts of retribution at his hapless would-be tormentors. But then we discover that it's not really Birsha at all, which does nothing to remedy the fact that a strong opening sections has been followed by a one that seems totally out of sync with all that has come before.

When magic is used as a substitute for the hard sweat-work of crafting characters with problems that they must confront and overcome through their own efforts, you deprive your reader of an essential discovery process as they seek to discover, "How's he gonna get out of this?" Oh. He pulls a rabbit out of his hat. YAWN.

Notice this comment by Chayna, after she's intervened on Birsha's behalf:

“This pill, one of many is a relic of my family. One of my ancestors was a witch. She performed in witchcraft, though she was not necessarily evil. She created these pills for people to reap what they sow, like karma.”

Up until that moment, you were doing a great job of letting your characters move the action along. In the process, you were prompting your readers to think, "Gosh, I wonder what's going to happen next." Provoke that curiosity, they'll remain your readers as they turn the pages to find out.

Then we hit that sentence. TIME OUT FOR EXPLANATION!!!! All forward momentum ceases in moments like this. In addition, you've forced your character to do your dirty work for you, an inevitable result of the first person POV. There is no other narrator than Birsha and so there is no knowledge outside his own frame of reference. But if you force your character to spoon feed information to your readers, simply because you can't find another way to convey what needs to be conveyed, you're not doing your job. Find that other way.

All that stuff Chayna's talking about is simply back story. Readers don't really care about backstory. They care about THIS story. The crucial information, from the reader's perspective, is that Chayna has access to the supernatural realm. The details don't matter at this point. Were you to give her something to do, rather than simply intone a speech, something that lets Birsha and the reader understand intuitively that this girl is plugged into higher currents, you would have accomplished your goal without breaking the reader's attention.

The second half, as I've indicated, is a problem and I don't think there's a tweak here or there that will fix it. I think you need to come up with a longer arc. What is happening is a significant development: Birsha's mind is being highjacked by a foreign entity, and yet you settle for simply informing us of this fact at the end. Here is where your first person voice could be effective, showing us the process by which Birsha loses himself. However you do it, you need to bring the reader along with you.

Still, it's a nice bit of writing, and I suspect there's a lot more where this came from.