How do I override a parent theme’s language files with a child theme?

you may use this below code for your problem:

  [1]: https://i.stack.imgur.com/5aX1D.png

or use below code:

add_action( 'after_setup_theme', function () 
{

    load_theme_textdomain( 'your parent theme name', get_stylesheet_directory() . '/languages/' );

    load_child_theme_textdomain( 'your child theme name', get_stylesheet_directory() . '/languages' );
} );