@cruunnerr
So after a couple of days I gave it a new try.
You were close to the solution. I did not install the dependencies right.
For all with the same issue, you have to read the instructions better than I did:
Navigate into your MagicMirror’s modules folder and execute git clone
https://github.com/ptrbld/MMM-Podcast.git. A new folder will appear
navigate into it. --> which means navigate into MMM-Podcast.
Execute npm install to install the node dependencies. --> in the folder MMM-Podcast, install the omx-manager and omxdirector (see dependencies).
3. Install omxplayer. --> However, I already had the newest version installed.
Now it works fine. And it is pretty awesome.
Thanks for helping me.
Mr.Coffee