It's okay for a first time. I've made a copy of it and added a few changes (they're in red). With more practice, you'll be a lot better at it.
Some points I want to note:
1) Past tense or present tense? Normally, my style is to incorporate as much of present continuous tense or present perfect (I followed the advice of a fellow translator). It's very hard, since Chinese doesn't have any tenses, but try to keep to one tense as much as possible. The only exceptions when past tenses are involved is when something has just happened or a dialogue.
Note the difference:
I say, "Let's go to the party!"
and
"Let's go to the party!" I said.
There's a lot of difference in this one. Because of the order differences, I have to change the tenses appropriately. You can have your own style. In fact, many translators prefer to use past tense exclusively because of how easy is it to translate it like that, but I got too used to this style that I just don't like to use past tense exclusively.
Also, you like to use past tense in areas when it isn't appropriate, like here:
"Accelerator was right-handed."
Of course, this is wrong, because at this point, Accelerator is still right-handed. This is why I prefer the present tense.
(Note: Accelerator has only one crutch on his right hand, so it isn't right to use 'crutches'.)
Of course, some of the editors would be rather picky about this. I have to thank my main translator, EngimaticRepose for his help here. Don't be afraid to make minor grammatical mistakes here, there are editors here to help.
1.1) Informal grammar.
As you noticed, I would add several apostrophes like "He's holding onto a gun."
This is because I'm treating this as a narration, rather than a text.
Using the above example, would you say "He's holding a gun." or "He is holding a gun."
Though the latter is grammatically correct, it feels awkward and choppy. You hardly see anyone saying the latter because it feels very rigid.
1.2) Pause whenever you need to.
As you know, English words take a longer time to say than Chinese.
Try reading this non-stop:
"Japanese girls wearing German uniforms exploring a Japanese music school in a Spanish town full of French people celebrating Chinese New Years in Switzerland shooting North African owls while piloting multi-legged talking demon slaying cloakable AMAZING GRACE SINGING 500mm coil gun firing "son of the god of fire" supertanks from the future."
Thank you, are you reading a tongue twister?
Pause whenever you need to, honestly. Add punctuations whenever necessary, especially fullstops. It's easier in Chinese to have twenty words per sentence because they have only 1 syllable, but what if it's in English? It'll be a disaster. I recommend only a maximum of 3 commas in a sentence.
(If you're wondering, the description above is about an anime called Sora No Woto.)
2) Content or grammar? Note that in this sentence: "不过，这个其实不成问题，四周日光灯发出的光线充溢着整个房间，拄着拐杖的他站在里面已经不知道多久了。" You can't translate it all into one sentence directly. Feel free to break up any sentences and synthesize them whenever you want to, as long as it doesn't compromise the content (Yes, I do take many liberties with translation, like in Vol 10 Epilogue, Laura said "Attention please!" while I translated it to "Hello, anybody in?", primarily because I'm not too focused on the dialogue as compared to the expositions, so try your best not to repeat my mistakes.
In this case, you translated it as "(...). But this isn’t becoming much of a problem, light flooded the room and Accelerator has already forgotten how long he has been standing there with his clutches."
For my case, I'll translate it as "... , but this isn't becoming much of a problem. Light floods the room as Accelerator has been standing inside for who knows how long."
Yes, I did a few edits, but you probably get the idea. Try to smoothen the edges as much as possible.
2.1) The content. Make sure you take in as much content as possible, even the seemingly meaningless words. In LNs (especially in TAMNI), minor details are extremely important. It's okay if you take a bit of liberties with the content (heavily not encouraged), but leaving out or adding is not a good thing at all. In particular, Kamachi-sensei pays a whole lot of attention on details (Must I mention that 'Fighting Fanservice' changing scene?), so remember to keep as close to the content as possible. It's a case of balancing grammar and content. The readers out there are sometimes very nitpicky about even the tiniest bit, and flame wars can blow up all because someone forgets to add a 'but' inside. (Sound like an oxymoron when you compare it to the previous point, but it's a case of striking a balance.)
3) If unsure, use a machine translator for phrases, or maybe a dictionary, or check out some other sources.
Remember, even if we're translators, we are not walking dictionaries. Machine translators may not be as accurate as one would like, but they're quite good for short phrases.
EDIT:
viewtopic.php?f=55&t=1737
The thread above has a link to some Japanese computer translators. Of course, I don't really know how many of these does Japan has, but feel free to use them as much as you want, but do not, I repeat, do not become too overreliant on them.
4) Don't copy any translator notes unnecessarily!
Very few people would like that in a dialogue, since though we're not professionals, we have to act like them (yes,it's very weird, but that's the class that people want to see).
Afterword:
Note that I'm not trying to undermine your ability, I just don't want to see my fellow translator get complains from all over the internet. It happened to me before in the Shana translation, and to be honest, it really hurts, even till now. A lot of guts and motivation is required to do this, more than manga and anime translation. I'm like a nasty sergeant here...
I admit, it's not easy, but persevere on! (Well, after your exams, at least.)
~Teh Ping
PS: When you're done, just upload it. If you still want me to recheck this one, use blue colour for your changes. (This is becoming like Umineko...). If you feel very uncertain about this or have any violent objections to it, we'll talk it out.
PS2: When you feel confident, you can go and register at the translator recruitment page. If you are uncertain about any sentence, we'll help out. Just post it at the TAMNI page here on the forums.
PS3: Why are people talking like there's only me? Joay is a lot more active now and is the better translator in terms of content.
PS4: I'll gladly accept any help! I'm sure Joay will too, but I need to tell him that first, since he's doing SS1 for now. (He said that he'll do SS1 and 15, maybe.)
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