The content remained in its original language. Not all of it was created in Ukrainian, but was translated into it. You can change it to Ukrainian only if there is no translation of this content. That is, you need to delete the translation and change the original language. Also, when you delete languages, translations are automatically deleted, and then you can simply specify the language and new text. For example, the menu item
Similarly, in sliders and nodes, you can change the original language.