lock on guess session

I can only access my laptop on guess session, I have lost my administrator privilege. somebody on this forum had the same problem as me, and I took the time to read through all the comments and follow the directions, but nothing works out for me.
I have pressed all the keys (Shift, Esc, Spacebar ...) I have read all the links posted on that thread and tried multiple time over and over again, how can someone help me, please?