My friends and I are translating some games and we want to know how to submit the translated version.
Thank you for your answer.

You need to contact the developers I think

Well, there's this thing called copyright, which prevents the distribution of works derived from copyrighted material without a corresponding license. In short this means that your translations, while a commendable effort, cannot be distributed unless the copyright holders of the respective game give their okay.

To have it actually distributed with the game itself, again you would have to rely on the copyright holders/developers adding it to their game.

In any case, GOG are not the ones to contact about it and thus do not have a submission process for this.

Reminds me a bit of translations for anime and games never brought to the west from japan. A thriving system where within a month you'd have fully translated anime/manga.

Offer the translation to the devs, maybe they will take it. Otherwise, offer it as an unofficial translation patch to the game as a download. That's about all you can probably do.

In case the publisher and dev are the same person. Sometimes they are not and you should instead contact the publisher since those often are responsible for the translation.

Since I was extremely disappointed about some German translations I contacted the devs and asked if they would be interested in a correction. In one case (Ether One: Redux) I also asked them if I could do a complete translation for them since I loved te game so much but it was only available in English and Spanish. They all were glad to get help from somebody who really knows the language in the case of "Tesla Effect: A Tex Murphy Advemture" however the publisher Atlus decided not to integrate my fix (which also corrected English subtitle timing and one bug btw) into the game so it is only available as a patch.

Anyway: search for contact adresses and just talk to them.

Another thing to consider is that the developers may only have use for such translations, if the infrastructure of the game already allows easy integration for different languages (preferably without having to mess with the code).