Lost all mail in gmail folders this morning

Hello,

I have lost all mail in my folders. Inbox, personal folders, delete folder. I was triying to create a new folders in gmail and Did but lost all mail in process. I am now getting new mail, just can't get by of the old. Is there a way to recover? I have years a personal mails I did not want to lose. Also I need to understand how it could have happened so it does not happen again