Great to have you here! Read the following guide on our developer zone to learn how you can help make this project better!
http://developer.piwik.org/guides/contributing-to-piwik-core
Please read the recommendations on writing a good bug report or feature request.
You can help improve translations in Piwik, please read contribute to translations.
You can help contribute to Piwik codebase via Pull Requests, see Contributing to Piwik core