I believe that workflows used to be packaged as .knime files that were basically zip files that you could unzip in the knime workspace folder. At that point, KNIME would recognize the folder as a workflow. So you could try that.
What’s the file size of that .knime file in your screenshot?
If it’s really small, then my guess is that it’s not a workflow. Instead it’s an xml file that lists the nodes and the connectors between them.
@elsamuel it is a small workflow, just one of the examples provided from knime
@mlauber71 it could open it after deinstalling the hole program (plus workspace, my partner copied it a couple times because he was so sorry and that caused a total error) and after reinstalling it I managed to open it via root directory;