You can manage your native and interested languages on your [Profile] page.
Once you have updated it, you cannot change your native language for 2 days.
As of April 2019, users may register up to 2 native languages.
 

Edit/Add languages and countries and regions>

  1. Tap or Click the edit icon on the top right of your screen
  2. Tap or Click your current native language or [Add another native language] or [Add another language of interest] or [Add another country and region of interest].
  3. Select a language.
  4. Select your level. (Native language and interest language only)
  5. Tap [OK]or Click [Save changes].

 

Edit languages level>

  1. Tap or Click the edit icon on the top right of your screen
  2. Tap or Click the level you want to edit.
  3. Select a new level.
  4. Tap [OK]or Click [Save changes].

 

Remove languages and countries and regions>

  1. Tap or Click the edit icon on the top right of your screen.  
  2. iOS  : Swipe left on the language or interest countries and regions you want to delete.  Android : Tap the option and (Delete) the language or interest countries and regions you want to delete.  Web : Click (X) on the language or interest countries and regions you want to delete. 
  3. Tap [OK]or Click[Save changes].