Photos and storage

So basically a few weeks ago I went to screen shot something (as you do) then later went to find it in my photos.. to find it wasn’t there.. so I went back to the website and screenshotted again to find the same thing happened. So I thought to myself maybe I’ve some how ran out of storage? To I went to settings for a closer look and it looks like I still have 75% storage left? So the next idea was to delete any photos I don’t want or don’t need and hope that allows me some space for more photos or screenshots etc. Right? — Wrong. I literally select as many photos as I want then press delete.. they disappear then as soon as I go back on my photos they’ve all reappeared again it’s so weird. I literally can’t take or screenshot anything because they don’t save and I also can’t delete photos or videos because as soon as I delete they reappear! So so so confused as to what is happening so any help would be greatly appreciated!! ☺️