IMO the brat was just an unlikable character added to the existing pair of unlikable characters. The art doesn't help either. Frankly, a sane person in my place would have stopped reading a while ago, but I'm too invested in the russian language mistakes.
Page 10 - no notes.
Page 11 - "to get nervous", infinitive, can make sense as a command, but obviously means the opposite of what's intended.
Page 12 - "to rest", infinitive, also makes sense if said as a command, extremely unnatural here, but the meaning mostly fits.
Page 13 panel 4 - not translated, a short exclamation usually meaning "whoops", but it's not too weird to use it like "hey" or "wow" or "hm", as seems to be the intention here.
Page 13 panel 5 - I don't want to rag on this too much, but the correct spelling is "хорошо" and while it does mean something like "good/great", it's a word without a grammatical subject, so the usage here is not correct, at least as far as mixing words from different languages can be correct. An adjective would fit more.
Page 14 - "excellent", fits the meaning well, no notes.
Page 15 - "[IGMS is] tasty". While one could come up with a male word that could fit ramen (which isn't grammatically male), it's way more natural to say something like the subjectless "вкусно".
Page 19 - an adverb that means "[IGMS that's been] bought". Tickets are grammatically male in russian, and I can see how this mistake could've been made, but it does sound weird af. "Купила" would actually fit here, meaning "I [female] bought [it]".
Page 27 - while the words for numbers are technically correct, in casual "counting up" situations where you're not actually dealing with numbers, the normal word for "one" is replaced with the casual "раз", which means "[one] time", as in one time, two times, three times (not multiplication). A weird quirk of the casual language.
Page 32 - a rare case of the author remembering to properly gender the words - Karen speaks about herself with a female form of the word. Unfortunately, it sounds unnatural. In russian, in cases like this, it's more natural to use verbs instead of adjectives. Something like "я боюсь", literally translating to "I fear/I am fearing", which now sounds unnatural in english.