How to change string which comes from breadcrumbs?
Your nodes contain apostrophe in their title. Node titles will be passed through check_plain() function and it uses htmlspecialchars() function to convert the quotes to HTML entities. 

You may try by decoding them back

function myowntheme_breadcrumb($variables) {
    $sep = ' &amp;gt; ';
  if (count($variables['breadcrumb']) &gt; -1) {
    return htmlspecialchars_decode(implode($sep, $variables['breadcrumb']),ENT_QUOTES);
  }
  else {
    return t("Home");
  }
}