Thank you for your answer! Actually, I want to adapt my project page for three languages, and I thought that having three projects with the same game isn’t really good.
There is not really multi language support on itch. Parts of the page can be set to another language, but not the projects. Maybe they will add this in the future, but currently, people just put their multi language description on the same page. Or more often, the description is in English and the game is marked as having several languages. There is also the issue of tags.
Pragmatically, people that do not understand english can just translate the page with their browser on the fly.