Download the language file from here:
http://www.question2answer.org/addons.php
Then extract into the languages folder in your Q2A installation, and then go to the admin center and change the main language.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.