Thank you for providing this translation @0spy !
Would we have your permission to include the translation in the next version of Nameless (the license the files are released under is MIT)
You will have to either restore from backup or run a MySQL query which you can build from piecing these parameters together: https://github.com/NamelessMC/Nameless/blob/v2.0.0-pr12/core/classes/Queries.php#L153
There should never be any need to remove a table from the database
The issue is caused when you leave the installer before finishing the process. You must complete the full installation otherwise this error will occur.
@felipesavazi Please see the "Broken API" section here: https://github.com/NamelessMC/Nameless/issues/2446
Following these instructions will resolve the issue for pre-release 12.
Also, I would recommend generating a new API key in the StaffCP -> Configuration -> API tab as this should be kept a secret.