I have this doujin. Do you guys mind if I upload all of it?
I have it in 2 language, Japanese and Chinese. I'd rather go with the original but the Chinese version got slightly better quality and shading. Which one would you prefer?

Oh, please do!
IMO, Chinese would be ok, since there are Chinese translators here. and Danbooru has high standards!

No to Chinese, since translating from Japanese to Chinese to English is not recommended.

Then I'll go with the Japanese one. It would be easier to translate too. I'll post the chinese one if there's demand.

Is it just me or I can't seem to upload it? Been trying for a couple hours now. Can anyone help?

It seems that I have to go half-size. Sorry for that.

Should I create a pool for this? For now I only use parent/child, but since I'm not supposed to do that should I make a pool even though it's still not approved?

Parent/child is rarely used for comics, especially when they're more than a few posts in length. Pools are always better for them even if they're never approved.