You can simply change "Questions" to "All Questions" in this line in lang files.
Once you do that, it'll be changed to All Questions. And to be sure that future update of Q2A do not change it back, you should follow the method for Customizing selected URLs or phrases.
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.