GitHub Git Versioning Workflow

Hello together,
I’m new to GitHub and still learning the best automation workflows. I would like to use as much automation as possible, and therefore I’m a bit confused about closing issues automatically on successfull merge of a pull request.

Some Information about my project:

  1. master is my default branch and is deployed to github pages.
  2. Each version (like next version will be 1.2) has its version branch (in this example “Version-1.2”).
  3. Each feature is developed in a branch based on the version branch (like “#99-Feature-99”).
    This has the advantage that the master is always ready for hotfixes.

Now I use the Pullrequest as follows:

  1. PullRequest merge version branch to master is normally a fast done pullrequest. It stays open very long.
  2. PullRequest merge feature to version branch (like “#99-Feature-99” to “Version-1.2”) contains the feature changes stays open only a little time until merged.

But with this project setup, the automation is not working. Issues are not closed automatically, even cards in project are not moving (I would like to have them “In Progress” when a Pullrequest to the version branch is created).

So, how do you others order your project? What am I doing wrong?