Nobu: That's not what I'm thinking.
****Should be: I'm not thinking that.
(The tone of Nobu's voice should not be in the passive here)
I'm sorry I made you think such horrible things. (this is good)
I really think she's only here for a short time. You're just thinking too much about it.
****Should be: "How long is she going to be her,"-- I was just getting a bit absorbed thinking about her.
(Mine is a bit awkward, but yours is just incorrect. Nobu is saying that he was getting absorbed into worrying about Hachi being there, nothing to do with Yuri-- and that is what pisses her off on the lower part of the page. If you don't get this across up here, it doesn't make sense on paper)
2
Yuri: Damnit - this is the worst!
sfx: vrooooom
3
Yuri: I complain but he thinks it's about her?
****Should be: Even when I'm complaining, he's thinking about her!?
(Get across the "Nobu's thinking about *her* and not ME" thought. If you want to keep "wake" as part of the translation, it would be: "In other words, even when I'm complaining, he's thinking about her!?" which would be more correct but sounds a bit awkward in English)
It would be better if he seemed to be fed up!
****Should be: It would be better if it was ME he was fed up with!!
(Mine is not exactly right either, but the important thing to convey is that Yuri is thinking that she would rather have Nobu be pissed off at her than be thinking about Hachi. In other words she's pissed that Nobu's not thinking only about her. Bold, italicize the word "me." While in Japanese we don't use self-pronouns that often, the strong implication is about ME, which has to spelled out for English speakers.)
4
Driver: Why don't you dump him then?
****Should be: Don't lash out at others every time you get dumped by a guy.
(You got the direction wrong, he's saying Yuri was dumped. I am not sure how you got what you did out of that line.)
The hell with him.
****Should be: I'm getting fed up with you.
(This is part of the humor, Yuri is going on about Nobu getting/not getting fed up with her but instead her manager says she's making him get fed up with her)
5
Yuri: I'm not dumping him!
****Should be: I am not getting dumped!!
(again, you got the direction wrong. The next part you did was wrong, so I'll fix it)
****Should be:
Driver (Yuri's manager): Why are you getting pissed-- even when I'm comforting you.
Yuri: How the hell (is that comforting)!??
(IE. Yuri's manager is saying he's already trying to comfort her, and Yuri is saying he's doing nothing of the sort)
Fujihara: Right now I should be working on my thesis instead of reading manga, but I love Nana. I'm pretty busy, but if you need my help I can lend it to you now and again (if it's for Nana's sake, haha). I'm not perfect at Japanese either, but I am 2kyuu, and Nana is not a very hard series to understand afterall.
Edit: This is what I get for just reading onemanga and not reading the raw, I am in the midst of reading the raw now. The translation is wrong in a bunch of places in ways that totally change the emotional connotations and interaction between characters. Since Nana is a manga that is ALL about emotions and interaction between characters (with rock in the background), this is a big problem. I am too busy right now to fix them, but you should go get some help.
Edit: This error was just so wrong that I can't stand leaving it be.
Nobu says (literally): "Even though --my real intentions that no one touched-- [Ren] was trying to listen to them for me, [but I still turned him away]."
In other words (connotations added):
-The pent up true feelings I had
-No one tried to understand them
-Ren though, was trying to ask me, trying to hear out my real voice
-Even though he was trying to reach out to me, I turned away (hungup)
The connotations here are important because even though Ren often treats Nobu like a little boy, we know that he does care about Nobu and shows it in his own way-- this is one of those points.
Maybe translate it as: Even though no one tried to understand my real feelings, Ren was trying to hear me out . . . but I . . .
Structurally this is totally different from the Japanese, but what's more important is to get the content and connotations in my opinion.
In any case REN, not Hachi, Ren was trying to hear out Nobu's real feelings. Because of this, Hachi says "Even though that was something I had to listen to."
This is the irony of the situation here. Ren was trying to hear out Nobu's true feelings, even though by all right that should have been Hachi's responsibility, and she's hearing this story now. In other words, Hachi is realizing that she all this time she was running away from Nobu when she should have tried to understand him at the time they found about her pregnancy.
This is why on the next page, when she asks Nobu "The name of the child . . . is Satsuki ok?" this line as a lot more impact in Japanese than your translation gives. The real thing Hachi is saying is, "I'm sorry I ignored you until now, I want to listen to you." For the first time since Takumi and her started living together, she has acknowledged that Nobu has a connection to her child, and is recognizing he is a part of it-- that he has a right to be a part of it.
So when Nobu says, "I'll teach the guitar," he's saying-- "Yes, I AM a part of this, I WANT to be a part." In other words, when he says "don't ruin my peace," this is just him drawing into the safe world he has created for himself, when his real heart-- his real heart was touched by Hachi when she acknowledges his place and responsibility to her child.
This scene is really beautiful, because it was like Ren was an Angel. Though it is undoubted that Ren's death was tragic, he said words that brought Hachi and Nobu to come to grips with each other's true feelings-- and not Ren, but Nobu who has a real place as father saying "I will teach the guitar." As in all right that is his place