Caveat: I Am Not The Best With Prose. But I will do my best.
First thing I notice is that you appear to have a problem a lot of beginning writers have. Perhaps it's due to the influence of visual media like movies and comics.
Problem is, a novel doesn't work like a visual medium. We'll tolerate a bit of time panning over a sweeping landscape or overlong action sequences in movies, but not so much in prose. Prose has different advantages, like the ability to communicate the subjective point of view of a character. It feels like these characters and events are being described from a distance.
I decided to dig into the sentence by sentence details of the latest chapter.
Use the name of the character in this instance, not 'she'. From this point of view we'd know her name.
I'm not sure I understand this sentence. Why 'even' when she was wearing 'only' black clothes? I think this means that the black clothes will absorb more heat and make her hot, but the message is kind of garbled.
Seems unnecessary to go into this much detail on her clothing. Gotta sneak descriptions in subtly. I notice that overemphasis on every piece of clothing a character wears, along with listing their physical traits, happens through the novel. If it's the pov character, find a sneaky way to work in their physical description. If it's another sort of character, try to focus on the important key traits.
I'm gonna use a bit from 'The Magpie Lord' 'cause it's my favorite book and no one can stop me.
Note the features that are called out here. We don't know anything about his shoes, or the colors of his waistcoat, but we do learn that his suit is cheap and ill-fitting. This tells us something about the character's background, and it makes sense for the point of vie character to notice it (a rich man who loves clothes). He's physically unimpressive, possibly unhealthy, has something strange about him, and hate the pov character Crane and Stephen will pop up in another passage I give as an example later in this post.
Too many uses of 'and' here. 'She enjoyed the feeling' is distancing, compared to just describing the feeling. For instance, .Also, overusing 'she' as a subject, even if that can sometimes be hard to avoid. If your hair is collected in a thick, heavy triple-braided bun, a gentle breeze won't pass through it.
It's unnecessary to specify that she went to a table in the garden after opening the door and stepping into the garden. Also, a lot is going on in this sentence (and in other sentences). She goes to the garden table, leaves her violin (which is called Beast), gets her tools, gets her white hat, and begins to work. Seems unsafe to bring her violin outside?
Should be 'had gained', and 'it had turned'. Again, too many ideas in this sentence. Should be 'at the very center'. 'recomforting' is either an archaic word that should generally not be used in prose or a misspelling of comforting. This sentence also confused me for a moment, because I didn't realize that the different plants and varied flowers weren't somehow being provided by the tree somehow. I read it as the tree 'providing a recomforting shadow and different plants...'.
If this character is a gardener, they wouldn't think of their plants as 'varied flowers'. They'd say 'petunias' or 'peonies'. A specific name for the specific flowers they planted.
No need to refer to her as 'the priest's daughter' here. We know her name. 'Nother big long sentence paragraph.
Pretty sure this isn't correct. The way the dialogue is formatted, I mean. Please go check out these blog posts from KJ Charles. Last quotation mark missing.
'she had a great amount of repressed anger inside her'
WHAT. Now, I admit, I didn't read the previous chapter, but literally this entire scene has been focused on this serene, relaxing feel. This is why it's important to get into a character's head.
If you're going to use homophobic slurs, make sure you're using them very, very wisely. It does not appear that this was used wisely. Should probably specify who is speaking here. Best not to leave that out until you've got dialogue flowing back and forth.
Looks like you don't know how to punctuate dialogue, so...
Go check out KJ Charles dialogue stuff that I linked earlier, but I can tell you basically that it should be:
"I am saying a thing," said KittyHamilton.
"I am saying a thing," said KittyHamilton, "and continuing to say that thing."
In other words, a ',' if it's going to be followed by a said. A '.' if it is the end of a sentence.
-Long sentences, long paragraphs. Potentially grammatically incorrect too when it comes to the sentences. It makes it harder for the reader to parse what is going on when so many ideas are shoved into one small place.
-Lack of voice. Now, there are styles that can can involve a narrator that is totally separate from the characters, but those are more like rare exceptions. For the typical, popular sort of story for a general audience, first person limited is the way to go, with the POV of the characters shaping the way things are told.
-Telling instead of showing. Now, admittedly this is kinda a stock answer, and it shouldn't be seen as a hard rule written in stone, but a general principle to keep in mind. 'enraging the woman' is a good example of telling instead of showing. If the woman was an unimportant minor character, or if this wasn't supposed to be a dramatic musical fight scene, it might not be an issue, but this is the main character of the scene having her precious garden destroyed.
I am by no means great at explaining how to write prose, and not great at writing it myself, but I've found this website useful.
I'm going to throw up a scene from one of my personal favorite novels here. I think it might be worth comparing handled the part where the serpent demon destroys the garden is handled to this bit of the book.
In this scene, a unknown magic user s trying to kill Crane by conjuring hair in his throat from an unknown location. Another magic user, Stephen fights this attacker by sending his magic through some of the conjured hairs.
This scene serves to put us in Crane's situation. The description of the expanding hair in his throat communicate how dangerous the threat is, and how it must feel to him. Then, the descriptions of Stephen magic, and how angry, determined, powerful, and frightening he is in this scene. All he does is touch Crane's neck and burn some hair, really, but the description sells the dangerous supernatural power at play.
While a scene like this let's me feel like I'm in the scene, experiencing it, a paragraph describing numerous elaborate effects is a bit like glancing at a TV with a movie I am unfamiliar with while walking ot the kitchen. I register what's happening, but from a distance, and without investment.
Other things...From the beginning, I think there's a lack of introduction to the world. An infodump would be bad, but a world this wildly different from our own needs a slower introduction. By the time Mercuria is on the train, I'm still not really sure what it means to live in a world where rock gives you magical powers. I didn't expect the dragon, or other unnatural animals to appear.
While you can communicate a wacky, fantasy, cartoon style in a cartoon, in a novel, people tend to default to 'realistic' unless the novel directs them to think otherwise.
I'm also having some difficulty with the action scenes, due to, I think, not understanding the rules of their music magic. Because I don't know the rules and limits of their abilities, the results seem a bit random?
The brisk movement of the plot is good. Bellaria has the potential to be interesting with her internal conflict.
I don't know if I'd call the characters flat, but the fact that they all kinda jumped on this trip to save the world willy-nilly made it harder for me to take them seriously. It's not weird enough for me to just shrug and say 'it's a weird story in a weird world', but not normal enough that I can take the desires, psychology, and safety of the characters seriously.
Phew, I need a break after writing this. I wonder if I have enough calories left in the day to eat a cupcake...