You can change it from the language file. in qa-include/qa-lang-main.php
If you want to change navigation title than find in array with nav_ like for As a Question 'nav_ask'
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask 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.