iphone's icloud photos are missing after update. photo app stucks in "restoring from icloud"

I had about 110,000 photos on my phone before the update to ios15. After that, I discovered that they all disappeared from the device: they were all uploaded to icloud, but now not a trace of them remained.  in icloud all the photos are in place, but they are not on the phone: I have about 30 photos left that simply were not uploaded there. is there any chance of getting my photos back to my iPhone?  or get it from somewhere?  the photos on my phone now take up about 20 GB, and I doubt that this is the real "weight" of 30 screenshots.  and if so, under what conditions can this happen?  and how long will it take?  i feel just awful: I don't understand why this could happen..