Change primary language in the new iTunes Connect

Apple recently released a new version of iTunes Connect. I just want to change the primary language of my app, but the documentation (https://developer.apple.com/library/ios/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/DisplayInMoreLanguages.html at the bottom) is now deprecated.

Anyone solved this problem?

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What is primary language in app store?

Primary language is the main language of the app. For all locals where you do not offer a localized version of your store listing, the App Store will automatically show your primary language.

How do I change the language of one app on my iPhone?

Change The App Language in iPhone or iPad AppsTap on the Settings app on the Home screen. Scroll down, select the app you wish to change its language. Select Language under Preferred Language. Choose the language you want to use.

Can you change the language for just one app?

Change the language setting for a specific app On your Android phone, open your Settings app. App languages. Select the app you want to change. Choose a language.

I was able to change the primary language after being accepted by the appstore.

Despite what the documentation says, it seems that changing the primary language is impossible in "Prepare for submission" state.