What about "Katerina's mother is no longer living"?
That works fine in English, and I have added it.
I entered this very thing (Katerina's mother is no longer living) and it was rejected.
There is no report in the system for it. But "Kateřina's mother is no longer living" tests "green," which means it should have been accepted. If that was exactly what you typed, you may have been bitten by the Duo grading bug.
Use "My answer should have been accepted". More often than not, people make some typo they do not see.
"... is noT longer alive" is not equal to "... is no longer alive"?
Your meaning would be understood, but the phrase "is not longer alive" would not be used in English. To use not, you might say something like "is not alive anymore" or "is not living anymore."
Can you explain the difference between using Possessive "Kateřinina matka" and Genitive "matka Kateřiny" in sentences like this? Thank you.
Can be use..... isn't alive yet. ?
To by znamenalo, že se matka ještě nenarodila. :-)