What is best way to translate labels in countdown element?

Hey Marcel,
Thank you for the link to your site, I’m not sure I understand your question but I see that your page language is [en-GB] and the content is in English, including the countdown element, please see the screenshot in the Private Content area.
The text for the countdown element is translated by the language files at /enfold/lang/, for example, in this screenshot the countdown element displays the correct text for the correct site language.

If you want to change the text to something else, I recommend changing the text in the translation files with Poedit, and save this in your child theme. You can do this for [EN] & [DE] if you wish.
To setup a child theme language directory, you would add a directory “/lang/” in your child theme and add this to your functions.php:

function language_file_child_theme() {
    $lang = get_stylesheet_directory().'/lang';
    return $lang;
}
add_filter('ava_theme_textdomain_path', 'language_file_child_theme');

and place your custom .po & .mo file inside.

Best regards,
Mike