Upload to iCloud stuck for days

I recently uploaded all my photos from my external hard drive to my iCloud drive. I did not sync them via Photos app but directly created folders on my iCloud and then copied the files from my external drive there. That was about 60GB of data. Everything uploaded smoothly; but for two days now the upload is stuck. If I click on the (i) next do iCloud Drive it says: 2,53GB of 3,71GB completed (Uploading 687 Objects). But there is no progress. I restarted my Mac several times. I also tried to "killall bird" via terminal. The progress remains the same. What else can I do?