Assuming that it is not a hardware failure, possibly the ram or the hdd, then opera's profile is probably corrupt. Backup your favorites, delete ~/.config/opera and start fresh.
@jimunderscorep
No, the bookmarks were lost as I said because I did restart of the system.
I've just tried to chown the whole folder and files of config/opera and now it works like with sudo, meaning bookmarks, sites logins, whatsapp, etc. are lost, but basic settings, history, etc. are now back again in normal mode.
I am just not sure if by default all of files of this folder are owned by normal user or some of them are roots one so that there is not any privacy leaks or sth.
In short, nothing at all.
The lack of borders around the opera's window is due to opera using its own csd and not the system's window manager, which (among other stuff like the min/max/close buttons) provides borders for the windows you have open.