Hi!
Adding a question from your survey to your library is super easy.
Inside the survey library you wish to add a question to, there is a green button near the top that says "Copy to this Library".

Once you click on that button a menu appears that prompts you to select which element (survey, question or block) you want to copy over, the source survey and source element, and where you want to store it in your library.

Hope this helps!

thanks a lot !