Help with proper language configuration

Hi, I need help with proper language configuration

  • it will be language other than English
  • it will be only one language
  • I don’t want language code in an address
  • it will be independent of a browser/system/IP settings
  • extra: I would prefer to have back-end in English

My config:

    - pl
  include_default_lang: true
  translations: true
  translations_fallback: true
  session_store_active: false
  http_accept_language: false
  override_locale: false

default_lang: pl  

And now I’m getting language code in site URL. getting system message in English on en language browser/pc/ip (and proper language on my smartphone). Also in “Sites” in Admin panel I have language code next to each site name.

P.S. What’s wrong with markdown on this forums?!

Ok so i figured how to disable language code in URL but i’m still getting system message in English.