The website is available in three languages. By default, the language in which it will be initially displayed will always be the preferred language for content that is defined in the browser. The language change is immediate by clicking on the language indicator that we see on the page where we are: In the worst case, there is always one at the bottom of the page.
If you want it to be displayed, initially, in another language, you must define that other language as preferred in the content language configuration of the browser.
The content of the site is not the same in all languages: This means that if we force the language change while viewing content (eg a news item) that is only in one language, we will find ourselves on the home page having changed the language.