Hi Nikolas Henke,
Go to https://sprintr.home.mendix.com/link/myapps under project management you can see stories->click more in the right corner ->import/export there you can import the stories.
Hello - I cannot find this either :-(. Can someone please help me?
It should be visible under
Project Management -> Planning -> 3 dots in the corner, and import.
If you don't see this, you might not have the correct access rights in the project, and should ask the project owner to give you at least product owner rights (or one with more access, like scrum master, or business engineer)