Update CONTRIBUTING.md

Making issue - implementation - PR process clearer

Co-authored-by: Michael Frey <michael.frey@gmx.ch>

CONTRIBUTING.md

@@ -14,7 +14,7 @@ We use GitHub to manage reviews of pull requests.
 
 * If you are a new contributor, see: [Steps to Contribute](#steps-to-contribute)
 
-* Before opening a new Pull Request, create an issue that describes the problem you would like to solve or the code that should be enhanced. Please note that you are willing to work on that issue.
+* Before implementing your change, create an issue that describes the problem you would like to solve or the code that should be enhanced. Please note that you are willing to work on that issue.
 
 * The team will review the issue and decide whether it should be implemented as a Pull Request. In that case, they will assign the issue to you. If the team decides against picking up the issue, it will be closed with a proper explanation.