The source language of framework is English.
After the installation, it seems like Crowdin integrated to KIWI, enables Russian language.
But I still need English. Disabling 'Translation mode' does not solve the issue.
How to turn on the source language?
The main language (aka server language) is controlled via the LANGUAGE_CODE setting, see https://kiwitcms.readthedocs.io/en/latest/installing_docker.html#customization for how to override those.
The Crowdin platform and the so called "Translation mode" makes it easier to update existing translations and/or add new languages by providing in-page editor, see https://kiwitcms.readthedocs.io/en/latest/contribution.html#translation, but has nothing to do with the language that is displayed to the user.
The language preference is actually taken from the browser settings and then falls back to the server language setting. If you want to disable this then remove LocaleMiddleware from your settings. See
https://docs.djangoproject.com/en/3.2/topics/i18n/translation/#how-django-discovers-language-preference for more background.
Disclaimer: this answer has been provided to you by a Kiwi TCMS team member.