For those who cannot finish meeting in Opera here the solution
We have to go to the button of Opera then Settings and Delete Private Data
Then we open a tab in which we have to do click Detailed Options and then Manage Cookies
We have selected own-free-website.com and then we click on Delet and then in Close.
Then we are going to Login and we have to be disconnected.
the process can help you to sign out in any website