I'm not gonna go through the whole thing because I can tell you know Japanese, but suggest reining in some of your liberties. Localizing text is fine (and necessary), but gotta be careful the original idea doesn't get lost in there.
Page 1 Your TL: How does that kill me?! JP text: ちょっと!また落とされたッ!? Author intent: Usually, I wouldn't care about this kind of liberty, but this is specifically related to Smash (where one dies by "falling off" the stage/ledge). "Hey, hold on! I fell off/was pushed off stage/the ledge again!?" // You did that all by yourself/jumped off yourself." I feel like the idea here is that she's so bad at Smash she doesn't even realize why she fell off lol She KNOWS jumping off kills her, but doesn't get WHY her character fell off (again).
Page 2 Your TL: Now seems like a good time to stop. JP text: さっさと本題に入るために終わらせたワケで? Author intent: Kinda missing the point here. "I just did that [on purpose] to put a stop [to the game] and [promptly] get down to business, though?" Omitting 本題に入る is one thing, but you're also missing the point where she tries to clumsily justify her loss.
Page 3 Your TL: There's no way I'll win. JP text: そういう提案するのか? Author intent: I feel like you spoke the implied part out loud, but it's not needed. It might make more sense if you change the other bubble too.
Suggested line to keep some of your localization: "Really? I bet you're thinking you'll crush me because you always get better grades than I do." // "Is that what you're going for/the [kind of] deal you're proposing?"
Page 3 Your TL: True JP text: そっ Author intent: It's actually just a stutter. そっ = そんな.
Page 3 Your TL: That would be kind of boring. JP text: そんなセコいことしませんケド~ Author intent: Another liberty I'd usually be okay with... if it captured the original idea, which is a cutesy "haha, there's no WAY I'd try to win by resorting to such a crafty trick! teehee" She's kinda bummed her very obvious plan got busted so quick, not that she's realizing her idea wouldn't be enough of a "challenge" as your lines implies.
@cutegyaru thank you. While translating I did feel like I was straying too far from the original text but I had trouble fitting my full translations into the text bubble and had to do some cutting.
Base +7, jsojoo12 -6, dankestdungeon -22, cathodex2 +6
@Antarenl That's the least of your concerns. If you have trouble fitting the text in bubbles, reduce the font size, change your fonts, play with kerning. Hell, you can even let it spill over and add a white stroke. (In fact, your text IS too big.)
Making an accurate translation should be your first, most important priority, and you should literally do everything to keep it that way. Editing is secondary.