Hello Rafał

Please share a screenshot of your issue to understand it better. Take a screenshot and share via any platform. For example: Lightshot or Imgur

Best regards

I took two screenshots. To make it easier for us to talk, one is green and the other, let's say, blue. In the green screenshot, the page is set to Polish language and the user is using the default Polish language. In the blue screenshot, the page is set to English language, but the user has set their language to Polish. As you can see in the screenshot, despite the translation, the user sees the English language. The problem is that on the page which is in English, the backend users use languages other than English. I hope it's clearer now. Here are the links to the screenshots:

Please follow this article

We clearly don't understand each other. Everything is correct if the page is in one language, e.g. Spanish. I mean front end and backend. In addition, we must assume that the administrator or editor also uses the same language, e.g. Spanish. The problem is that some of my admins don't speak the same language as frontend and backend. In such a situation, they have the option of setting their own language other than the entire page. In this particular situation, the translation does not work. It shows the set translation that is in the Joomla system as the frontend and not the one set by the user. The site is in one language, it is not a multilingual site. Only the admins and editors speak a different language than the entire site.

Apology for the delay. Please record a screencast and share here. It will be helpful to understand the issue. Please follow this article if you want to make the site multilingual.