A survey is a template that can be re-used in different projects. A survey is added to a project when the project is created.
When a project is launched, a copy of the entire survey, including the rating scales and themes will be created. Editing or deleting the survey template will not change the survey in a launched project.
If you need to change the survey content, the best practice is to edit the survey template and relaunch the project. However, in need, many elements of the survey content can be modified in the live survey project.