Hello @Nataša7, you are at the German community and usually we get just questions in German from other hosts to inform them about rules, help and procedure from airbnb. As a Superhost I hade this kind of issue once.
It's up to you to refund the not refundable amount from a guest who canceled and didn't arrived.
You can decline it without writing of reasons. You can offer a refund just if you get a new booking during this periode (for the new booked days).
If the reason of the cancelation is covered from airbnb with a doctor's letter, airbnb will refund directly to the guest all and you are not entitled for a payout.
You can find more details on the help center of you search about illness cancelation.
Happy hosting...