WP Customazation API doesn’t save the default Value

No it does not, its mainly for demo purposes within Customizer.
If you want a default to be output, in your output do this:

echo get_theme_mod( 'text_setting', __( 'Default value here', 'text-domain' ) );

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