Re care homes abroad, if people have dementia and the local language is not their mother tongue, it’s not at all unknown for people to lose the knowledge of their 2nd language, even if they’d been reasonably fluent.
The memory has been likened to a stack of bookshelves. As dementia progresses, memories are gradually (or fairly quickly, according to how the disease progresses) swept away, starting with the ‘top shelf’, i.e. the newest. And that includes the memory’s language skills.
I’ve heard of this happening with elderly Asian people in the U.K., who had forgotten their formerly very good, or perfectly adequate English, and could understand only their mother tongue.