Hellenic Mapping

This has happened 2 times today and it keeps freezing. Any tips on to how to stop this? The first time I had to do it all over again. I can't risk it again now

I was working on a project and where which picture had tons of layers, and I had suddenly tried to save one where it froze like that for an hour. i tried solving it but nothing happened so i just closed the program. now, ive lost all the layers because it was a .png file (i did undo to continue the project and receive back again the layers). Is there any way i can get the layers back? Ive made only 3 .pdn files which wont anyways help me at all