"No, I have not sold the apartment yet."
Translation:Ne, ten byt jsem ještě neprodala.
Thanks a lot for this! Spanish is my mother tongue and sometimes I find Czech closer to Spanish, such as před would be the same as hace (před týdnem/hace una semana). Actually, this už/ještě thing would be valid for Portuguese (já e ainda), Italian (gia e ancora) and French (dejá et encore). With před is more complicated because the word order is different, but Spanish and Portuguese are the same in this regard :)
I had a similar problem with using "už" when it should have been "ješte."
VladaFu gave me a great explanation, which you can find here: https://www.duolingo.com/comment/26862763$from_email=comment&comment_id=26867011
I haven't fully digested it myself, but there's a lot of useful information there!