An ordinary uninstallation of Opera, like with a variety of other browsers, does not remove certain of its files/folders that contain personalized data or settings. The good news with this uninstall approach is that this allows a later re-install of the browser to automatically access the user's customization and personal data, assuming the browser is reinstalled to its 'ordinary' folder-name location. The bad news is that there are various browser settings and data files that, if they had become corrupted or became hopelessly entangled with conflicting settings in the prior installation, will automatically carry over into the new installation - as will some or all of the previous problems.
The best approach I've found to get a truly clean installation is generally, with the browser off, to backup the browser's profile folders as a unit into a unique-named folder by copying. Then uninstall the browser and delete all the folders that are related to the browser (except the newly-created backup folder). This will assure nothing is carried over from the prior install into the new installation while preserving a copy of the previous user files. Perform a new, fresh install of the browser and test it to verify the previous problem(s) have departed. If any of the problems recur at this point, then the problem cause resides in something else on the system or, indeed, in Opera itself in the way it is installed on that system. Finally, start applying customization of the browser. I usually begin with my customization of the browser's internal settings, check for problem recurrences, then add extensions one at a time, testing for problems after adding each one. In my own case, I then re-import my bookmarks from a single reference bookmarks html file I maintain for use with all my different browsers, kind of like a personal sync function. Other users have their own methods and preferences for setting up the new installation to one's personal taste.
The point of creating a copy of the user profile folders/files is that one will always have a path back home to the state of the previous installation (and perhaps its problems) if that becomes necessary for whatever reason. Simply install the browser to its original location, turn it off, and copy the backup folders/files to their original locations in place of the new installation's files.
Finally, just a few words of advice on posting etiquette in a volunteer forum. First, keep an attitude of humility and respectfulness when posting about problems involving software you've paid nothing for and whenever asking for help from others who are also paid nothing for their time, knowledge, and effort. Second, remember that responders are human - their wording, detail level, or phrasing may not be clear or seemingly responsive at first. So always dialogue with an open mind toward getting to a useful solution without alienating or criticizing the person who's trying to help.