Hello, Emmanuel.Teyssier. Welcome to the Wikimedia Meta-Wiki! This website is for coordinating and discussing all Wikimedia projects. You may find it useful to read our policy page. If you are interested in doing translations, visit Meta:Babylon. You can also leave a note on Meta:Babel or Wikimedia Forum (please read the instructions at the top of the page before posting there). Happy editing!
You signed up on the Wikidata volunteers page as someone who's interested in coding. We've finally gotten things figured out and started with a few tasks. More will follow soon. You can find the current bugs/tasks here. If you decide to work on one of them please leave a note in the bug report saying so. Let me know if you have any questions :)