Can't save about us page

I duplicated your about-us page and made some changes, update and closed the window, went back to the dashboard and the about-us is gone, but I have a John Davenport page.
Is it forbidden to use your demo pages as a practice area for a new person like myself?
I made the change to enable more memory, I tried to change the author, but the same results, can you tell me what is going on please?