“Project Gutenberg“ is a website ion which many literary works whose copyright has expired is openare accesible to the public.

"Open" to me implies that the words are something physical, like a building or door, instead of digital.

“Winnie-the-Pooh” which I'm thinking of reading in English, whas alsobeen published there.

Same as “Project Gutenberg,“In Japan there is a website called “青空文庫 (Aozora bunko)” in Japan, and it is similar to “Project Gutenberg".

Their works are hard to read, because old works use also old expressions, so I think it is not righteasy to read them for entertainment.

"Right" does't really make sense here.

I am concerned that the expressions of the works in Project Gutenberg may be old same as, just like on Aozora Bunko.

But I'm not aso familiar with English, so it might not bother me.

“Project Gutenberg“ is a website in whichwhere many literary works whose copyright has expired is openare available to the public.

The website is a place where things are kept so I substituted "where" for "which."

Verb agreement
Sentence breakdown: ... many literary works ... are available ...

“"Winnie-the-Pooh”," which I'm thinking of reading in English, wascan also publishedbe found there.

Same as “Like Project Gutenberg,“ there is a website called “青空文庫 (Aozora bBunko)” in Japan.

そうですね。

HI, however, I rarely use Aozora bBunko.

We avoid beginning sentences with "however" in written English.

Their works books they have are hard to read, because old written works use also ols dated expressions, so I think it is not rightthey are not good choices to read them for entertainment.

We used "dated" to describe outdated expressions.

I am concerned that the expressions ofused in the works in at Project Gutenberg may be old same asdated the same way they are at Aozora Bunko.

But I'm not aso familiar with English, however, so it might not bother me.

“Project Gutenberg“ is a website in which many literary works whose copyright has expired isare open to the public.

This is correct but is very formal. "Project Gutenberg is a website where you can access books when their copyright has expired" means the same thing, but is an easier to read sentence.

“Winnie-the-Pooh” which I'm thinking of reading in English, was also publishedI'm thinking of reading Winnie-the-Pooh in English, which has been published on this site.

Same as “Project Gutenberg,“ tThere is a website “in Japan called 青空文庫 (Aozora bunko)” in Japan which is the same as Project Gutenberg.