If you use English as a default language then create this directory qa-lang/custom and copy the file from qa-include/qa-lang-emails.php to that directory. Then modify the qa-lang/custom/qa-lang-emails.php file accordingly
If you don't use English as a default language email texts are stored in qa-lang/<your-language>/qa-lang-emails.php.
Regarding changing the url, that will be a bit more difficult, and I can't figure out why you would do that. The url is already generated for you. What would you change exactly? What's the current url you get and what's your expected url?