How does translation (gettext) work for translating config file of plugin?

WordPress doesn’t automatically translate anything, you need to use the __ and _e functions, even in your config file, if you want it to be translateable.

define( 'CONSTANT', __( 'some string', 'textdomain' ) );

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)