Hello Thomas Ervik
Welcome to Microsoft Q&A Platform, thanks for posting your query here.
As the upgrade was successful in other regions, it's possible that the issue is specific to the node pool in Germany West Central.
The error message you are seeing indicates that the SKU of the node pool is set to "Basic" while the kind of the node pool is set to something else.
Try these troubleshooting steps to resolve this issue, you can either set the SKU to match the kind or remove the kind setting altogether.
If the issue persists, you can try removing the kind setting from the node pool and then running the upgrade command again.
After removing the kind setting, you can run the upgrade command again.
Hope this helps.