Unsaving photos from icloud

So my iCloud storage on my iPhone is almost full and almost all of it is from my photos. I didn’t know this but I think when I first got the phone it automatically started saving my photos to my iCloud. I don’t need or want my photos saved to my iCloud as I would like that storage space for other things. Currently I have it turned off so it won’t save them to my iCloud any further but I still have all my previous photos taking up a ton of space in my iCloud storage. So I looked into pressing “Turn Off and Delete from iCloud” (Settings->Apple ID->iCloud->Photos->Manage Storage) but I’m nervous that all of my previous photos will be lost. It says that I have 30 days to download my photos and videos from the iCloud but where do they go? Do they stay in my photos app? Or do that go into my downloads? If I go through with it am I able to undo it if they disappear? Sorry for all the questions, I’m just worried. I don’t need the previous photos saved to my iCloud but I still want them. If anyone can help me I would really appreciate it, thanks.