how to completely uninstall

I uninstalled the plugin because it was giving me problems with the 404.php page.
I tried to reinstall the plugin by clearing before all the caches on the service worker but it seems that the uninstallation is not complete as the set up form in the admin side control panel of the plugin always shows the old settings even after uninstallation. Does the plugin write data to the database? Is it necessary to clean data from the database to uninstall it completely? Possibly which records of the wordpress database must be deleted to uninstall the plugin completely and then launch a new clean installation?

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