The "'da" suffix is locative, "Ankara'da means "in Ankara" so you can't lose that in translation. "Var" by itself also doesn't show possession, it just means "there is", it can be used to show possession if you say something like "There is my X", or in this case, "There are Ankara's lots of cats". I believe it'd be something like "Ankara'nın çok kedisi var", and that's only if Ankara literally owns the cats.
Anyway, "Ankara'da çok kedi var" can mean the same thing as "Ankara has a lot of cats", but it is important we understand the difference, and this is a locative lesson, so we have to translate the locative.
I couldn't find the examples I had before. I know they were somewhere on the turkish -> english duolingo. I think I remember one like "bende kizlar" = "I have the girls" or something. And it seemed like if you had some something, you would use the possessive, but if you had specific ones of something, you would use -de.