I need a confirmation from who bought the game.
Is the GoG versione the multilanguage ones or the only Us ones?

It is multi language, cannot remember them all at the moment but there are 5 language choices when you start the game.
HTH

English, French, German, Spanish, Italian, Dutch are available languages to choose from ;)

I ask then to the GoG team to update the game page to consider that. Even in Prince of Persia if it's the case (I can suppose it is if BG&E is because european version of PoP is multilanguage).
Thanks

No, Prince of Persia only includes english language files. The thing with BG&E is that you choose the language AFTER starting up the game, but I agree with you that this should be pointed out for BG&E.

I'm pretty sure there are only multilanguage version of PoPSoT out there, the problem here is that you have to choose a language before installation occurs. Lucky thing that the languages are embeded in BG&E. I hope GOG consideres multilanguage support for their games.
What languages did the Italian version of PoPSoT contain ?

But the problem is not the installaton but the license that is the thing that prevent GoG to have all language for every game because it have to sign different agreement with local publisher in some case. But Ubisoft has the rights for the multilanguage version so GoG could have added all the language. The option are: a large installer with all the language and the option to select the one you need (i like this) or smaller installer for every version.
Not sure but however Italian, French, Dutch, English, and maybe Spanish. I have always bought the multilanguage version because I like to play the game in its native language and give a chance to my language dub. The problem is that only SoT was done right, the sequels had an awful dub.

It's important to put it on the game's page that it's multi-language.
I usually prefer my games in english, but as this one is a french one, I prefer to play it in french.
Update the game's page please! :)