Hello Schwaben10,
Thanks for using the Apple Support Communities!
I understand from your question that you would like to to import photos from your iPhone to Photos on your Mac, but Photos doesn’t appear to see any photos that are on your iPhone. Were all of the photos you are trying to import taken on the iPhone or were they synced to your iPhone from a different device?
The attached article explains that you can’t import photos or videos that were synced from iTunes which could explain this behavior.
Import photos and videos from your iPhone, iPad, or iPod touch to your computer - Apple Support
You may also be using or choose to use iCloud Photo Library. This service will keep all of your photos up to date across all of your devices. For more information about iCloud Photo Library, please read over the next article.
iCloud Photo Library FAQ - Apple Support
Cheers!