how to change the admin lang. back to english without access to the panel

[lat9]

Go to your webhost's cPanel and, from there, to your phpMyAdmin.

Click on the SQL tab and enter

UPDATE configuration SET configuration_value = 'en' WHERE configuration_key = 'DEFAULT_LANGUAGE';

If your site uses a DB_PREFIX (like zen_), the SQL would look like

UPDATE zen_configuration SET configuration_value = 'en' WHERE configuration_key = 'DEFAULT_LANGUAGE';