I’m sorry that I didn’t explain myself cleary. I was very confused as it was.
I already solved the problem, in case you don’t want to read the explanation.
Here is what I was trying to do:
I imported about 20 photos to the library from my iPhone with iOS 11, first import after updating to High Sierra.
After that, I added the photos to the albums that I wanted, but somehow they got mixed and a bunch of them ended in different albums than I had put them into, I’m pretty sure I put them all in the right places. So I tried to delete them, just from the album (delete) not from the library (command + delete) and it didn’t work. The computer didn’t respond. But if I tried to delete them from the library it worked.
I solved the problem by deleting them all from the library and importing them again from my iPhone. I was having a lot of trouble with duplicates from JPEG and HEIF at the time, didn’t know what was causing the problem.
Thanks for you answer anyway!