@sirlinx I found a way to fix it. In the Appdata/Roaming, there's a folder called "Opera Software" and inside of it is "Opera Stable". Then find the "Preferences" file and edit the string thingy called "window_placement_video_popout" then change the "height" and "left" that you want. This allows you not to lose your history, cookies, passwords and etc.
I hope this helps you