On the Android app, it currently offers only one "the". I got it correct by guessing it should be put before "rich part", but I would normally use one before "town" too, just like in Swedish.
Why did it fail me with city when it is perfectly stated that city is an option?!?
That depends, what did you put exactly? Note that English can use either "town" or "the town", but only "the city" and not just "city" here. So if you put just "city", that's the reason.
I wrote "He lives in a rich part of the city." Marked wrong. That's wrong?
den rika delen is in the definite, so it's "the rich part". I'm assuming whatever city it is has one rich part and at least one that, well, isn't rich.
"a rich part" would be en rik del instead.
Det chica området
Any chance this could be translated as "He lives in the rich section of town?" Or is that too colloquial?
why not "the town" if we have "staden" in definitive form?
We do accept that as well, but just "town" is more idiomatic in English.