Workflow to add a sprint to a new issue Follow

Hello,

For quite a while I am trying to add an issue of the state New automatically to the current sprint of a defined agile board (if there is no sprint set jet).
To check and change the sate is clear to me, aswell as the if-case to check whether the issue field has already a sprint set or not. 

But how can I get the current sprint of an Agile board as a variable into my workflow?

And how to set this to the sprint field of an issue?

Hope you can help me with this request.

Thanks in advance!