I love this series and I've read it up to ch 100 or so, I know the MC is unbearable at the beginning but the story is really good so stick with it. I'm glad somebody is taking the time to translate the series for the English audience, but the translations aren't very accurate, it misses out on a lot of dialogue. Some of the more important ones that help with characterization:
In chapter 1 (at the end) Minwoo is cussing "I (fucking) told you to speak, and you actually (fucking) spoke, but your pronunciation is really (fucking) great, hm?" He cusses a lot when he talks in most of his dialogue.
In chapter 2 she's not saying "I'm not going to see him" she's saying "I'm not going to just let him get away" (like she did with the first dude who transferred to another school). When he woke up and saw her there was "Embarrassment, fear, AND disgust". She doesn't say "Oppa we've met before" she says "Oppa let's date". She doesn't think she's giving up on herself to keep him she thinks "I'm gifting myself to oppa (slave basically), sacrificing myself is the only way to keep oppa". She doesn't think "I'll cheer him up tomorrow" she says "I'll work hard tomorrow too". She's also more aggressive towards Yoona "Mind your own business Woo Yoona".
In chapter 3 she notices that "He goes out often at night for several days at a time, and he showers before coming back." It's not "I kept it back on the table to make it less obvious (???)" it's "He left it on the table on purpose". Her monologue "I have to make a choice, oppa I don't want to let you go....etc" is actually "I have to make a choice, do I let oppa go or beg him to stay even if if things are like this (he's cheating) it doesn't matter". His break up "You still don't (fucking) understand the situation, sitting here with a fat (fucking) pig like you is a big deal. I've already put up with you for 2 (fucking) years, it's time for you to leave." The reason why she decides to dump him but then tries to hang on is solely because he showed up in a suit and she thinks it's hot "You leave me no choice" L M A O. Then he slaps her and runs off (this whole situation is so absurd it's comedic) and she thinks “Oppa is fleeing, as if he's avoiding a cockroach" not "Running away like a leech".
So yeah these characters are all much more awful than the translation makes them sound.
Edit: this is in no way an attack on the translators, they're doing good work, I just wanted to help flesh out how truly awful these people are.