Quark theme's language

I added a new language section to quark's language.yaml based on the english's structure and even after deleting the cache I still get SIDEBAR.POPULAR_TAGS.HEADLINE strings on the page. The default lang is set accordingly as set in the language.yaml section. What am I missing?

... actually I'm not using Quark directly but through https://github.com/hibbitts-design/grav-skeleton-open-publishing-space

To be more precise (and maybe of help to the quark translation) this is my addition to the languages.yaml:

hu:
  TRANSLATION_TEST: Quark!
  BLOG:
    ITEM:
      CONTINUE_READING: Tovább olvasás...
      NEXT_POST: Következő bejegyzés
      PREV_POST: Előző bejegyzés
  SHOP:
    ITEM:
      BACK: vissza
      NEXT_ITEM: Következő
      PREV_ITEM: Előző
  SIDEBAR:
    SIMPLE_SEARCH:
      HEADLINE: Keresés
    RELATED_POSTS:
      HEADLINE: Kapcsolódó bejegyzések
    RANDOM_ARTICLE:
      HEADLINE: Véletlenszerű bejegyzés
      FEELING_LUCKY: Áldottnak érzem magam!
    SOME_TEXT_WIDGET:
      HEADLINE: Widget szöveg
    POPULAR_TAGS:
      HEADLINE: Népszerű címkék
    ARCHIVES:
      HEADLINE: Archívum
    SYNDICATE:
      HEADLINE: Szindikátus
  FORM_DATA:
    SUMMARY: "Itt egy összegző arról, hogy, mit írt számunkra:"
  ERROR: Hiba

@obeliksz I have downloaded the skeleton and tried the following:

1. In '/user/config/system.yaml' added Hungarian (hu) to the list of supported languages.
   YAMLCopy

   languages:
    supported:
      - hu
   

2. In '/user/config/site.yaml' I added Hungarian as default language.
   TXTCopy

   default_lang: hu
   

3. In '/user/themes/quark/languages.yaml' I added your section for Hungarian.
   YAMLCopy

   hu:
    TRANSLATION_TEST: Quark!
    BLOG:
      ITEM:
        CONTINUE_READING: Tovább olvasás...
        NEXT_POST: Következő bejegyzés
        PREV_POST: Előző bejegyzés
     ...
   

   The sidebar now shows 'Népszerű címkék' as title of the Popular Tags.

My installation of user/cofig/system.yaml has no supported part in its languages section, but I added it as you put it:

languages:
  include_default_lang: true
  translations: false
  translations_fallback: false
  session_store_active: false
  http_accept_language: false
  override_locale: false
  supported:
    - hu

In the site.yaml I removed the apostrophes '' from 'hu'.
Deleted the cache, still same SIDEBAR.POPULAR_TAGS.HEADLINE.

Thanks, will check on a completely new installation and try to find out what goes wrong by comparing to it.

Got it solved by changing to true in the previously quoted languages: section's translations part.

And not sure if that had an effect on it but changed the theme from quark-open-publishing to the default mytheme.

But now as I have the supported: tag, I get an extra locale indication in my url which I don't want as it is not multilingual, can I get rid of it, how could I go about removing it?

Thank you for helping me to a solution on this, learned from you! 😃