iCloud and gallery photos

Hello, I had 40k photos on my

phone forever and I was too lazy to delete them all. Today I decided to delete them, finally half of them was gone, but there was still one problem. iCloud. It takes too long for me to pick and choose all 20k pictures from iCloud and delete them as well and if I turn off iCloud photos from my settings, all my pictures that I currently have will be gone and by turning it back on I'll get the 40k pictures I previously had which I don't want. Please tell me there is a way I could sync my gallery photos with my iCloud or something so I don't have to be deleting everything all over again. Thank you in advance.