The main page of the game present 10 languages translations for each episode, why here on gog this stuff isn't available?

While the developer does offer a variety of language options when playing the individual episodes directly through their website, the retail released "Collector's Edition", which is sold on , [url=http://store.steampowered.com/app/284390/]Steam and many other online retailers, only supports English and Spanish.

If you would like to see more languages supported by the retail version, you could always contact the developers and make a request.

The only official languages for this game are english and spanish, other languages are community-provided, that's likely the reason.

And by the way, while I don't know for the rest, I can say the french translation really feels community-provided, unfortunately. I suppose I should do one myself, but I know for having translated someone's résumé once that a good translation can require a fairly big amount of work...

EDIT : There are two french translations available eventually, my comment was targeting the first and most easily accessible one. I started the second one (from paperyoshis), which is clearly better as far as I checked it.

News about additional translations for the CE and the upcoming second season CE can be found in this short thread:

https://thelastdoor.com/forums/viewtopic.php?f=4&t=3425&p=8362#p8362

"Hi,
we are working in updating the Collector's Edition with more languages, in preparation for the launch of the new Season on those plataforms (GoG, Steam and mobile).
There are numerous changes and optimisations on the Collector's Edition, which prevents us to directly utilise the community based translations of the browser episodes. But we're working on it.
regards."

And here you can see the latest news (additional languages ARE coming to BOTH seasons soon):

https://www.gog.com/forum/general/release_the_last_door_season_2_collectors_edition_377bc/post23

Aaaaand it will still take a bit according to Katy from Phoenix Online (publisher):

"Sorry for the delay in responding. They're still bug fixing, some OS updates introduced new issues that needed to be addressed. Again, these should be completed and ready to release soon!"

The wait is over!

Both seasons have been updated supporting additional languages and I've posted the changelogs here.