Page 9:
"Well, if you apply it officially, the problem is..."
This is clearly a math problem being discussed in the classroom, which you know because Yamamoto replies with a number when called on by the teacher.
公式に doesn't mean "officially" here as an adverb, 公式 is a noun, and the に followed by the verb 当てはめる is the action being done to it. In the context of mathematics 公式 can mean "formula" in english. "Well, If you apply it to the/this formula" is likely a correct rough translation.
"Oh, I don't know if that's the right answer or not"
The teacher in japanese says おぉ 正解 まさか解けるとは
The おぉ there is exclamatory, expressing that he's impressed. It's hard to tell because manga loves not using punctuation in dialogue, but the 正解(correct) following it is meant to be the end of a single sentence, which is why in the original japanese there's a line break there. He's telling Yamamoto he got the answer right.
まさか解けるとは is an example of standard japanese practice where they don't finish sentences because the ending is implied by the part of the sentence spoken already.
In this case, he's basically saying that he didn't expect Yamamoto to solve it, and the fact that he did is surprising. We can assume Yamamoto's probably a bit of a slacker or dumb.
"Huh, that's correct. I didn't really expect a right answer from you" is a summation of what he's saying.
I noticed you didn't translate the sound of the students laughing at him either. You should have, it's important to Hori's reaction there. She's scared of being laughed at like that which is why she gets nauseous on that page.
on page 30:
"It's already yakekun!" is completely wrong lol
In the raw she says もうヤケクソ!(Mou yakekuso!). Mou in japanese can mean "already" but is also an exclamatory phrase to express annoyance or frustration. It's the latter in this case. Yakekuso (not yakekun, get better at distinguishing between ソ and ン) means desperate.
In other words, she's essentially saying she's out of ideas so she'll give up and go with the goth loli clothing. "Screw it", as it were.
There's almost definitely loads more errors in this translation but i just skimmed it really quickly and pointed out the two that were egregious enough to be obvious mistranslations.
imo work on your understanding of jp grammar and if you can't come up with a translation that makes clear sense to you and your readers (like the mistranslation on page 30), google more deeply or think harder about the sentence til you really understand it or you're not gonna improve