Hello, QUestions like the one you have asked have already been answerd in the forum prior to this. Please search through for finding out many other use cases of url changes. Anyways, for your specific requirement you need is this:
1. edit qa-config.php file
2. un-comment the $QA_CONST_PATH_MAP section and add the new urls for the default urls in that array. So for your requirement add an entry like "ask" => "post"
Now for changing the Question page title, you can do so along with others in the qa-lang-main.php file inside qa-include folder.
Please let me know if this helped.