Query monitors alerts about 2 PHP errors

NoticeUndefined variable: user+

1. wp-content/themes/sacconicase/functions.php:699

1TemaNoticeTrying to get property ‘ID’ of non-object+

1. wp-content/themes/sacconicase/functions.php:699

1Tema

NoticeUndefined variable: user+

1. wp-content/themes/sacconicase/functions.php:703

1TemaNoticeTrying to get property ‘ID’ of non-object+

1. wp-content/themes/sacconicase/functions.php:703

Line 699 is:$german = get_the_author_meta('periodo_affitti_de', $user->ID );

inside

add_shortcode('periodo_affitti', 'translate_rent');
function translate_rent() {
  global $post;
  $german = get_the_author_meta('periodo_affitti_de', $user->ID );
  if ( 'de_DE' == get_locale() && ! empty( $german )){
     return $german;
  } else {
     return get_the_author_meta( 'periodo_affitti', $user->ID ) ;
  }
}

Line 703 is inside the same function

When I have “return” I dont know how to fix the function

The page I need help with: [log in to see the link]