Hi there, can understand how frustrating this can turn out to be at times, i believe this error has been caused due to some incompatible or outdated plugin, assuming you have access to cpanel and can get bit techy, what i suggest to you is try disabling all the plugin and try again, most of the times i believe in your case it will work for sure.
Well just to make things easier sharing you a link, try logging into cpanel and then MyPhp admin and follow the mentioned steps.
Here you go, Wish you luck !
https://www.wpbeginner.com/plugins/how-to-deactivate-all-plugins-when-not-able-to-access-wp-admin/