Thanks @johanhermansson for the snippet. If somebody needs to allow modify fields from child theme this snippet works for me:
add_filter('acf/settings/load_json', function($paths) {
$paths = array(get_template_directory() . '/acf-json');
if(is_child_theme()){
$paths = array(
get_stylesheet_directory() . '/acf-json',
get_template_directory() . '/acf-json'
);
}
return $paths;
});