"They hate themselves because they did bad things."
Translation:Kendilerinden nefret ediyorlar çünkü kötü şeyler yaptılar.
I am confused by this as well. It has been explained repeatedly that we cannot use -lar/-ler on a general direct object (https://forum.duolingo.com/comment/7736911). Here it seems like "bad things" is actually a specific direct object, because it is the specific things that they did that made them hate themselves. But the answer calls for kötü şeyler, and considers kötü şeyleri a typo?
In that thread, Ektoraskan (whose words are considered 'gospel truth' among course moderators) states that the plural suffix actually can be used. The pluralized thing is then explicitly not specific.
He says: "It's either hypothetical or you emphasize the multiplicity or the excess."
Hapzelschnapper, thanks for Ektoraskan explanations (i forgot) we really don't know the context of the English sentence we have here. Perhaps a conversation between several persons who heard or read about those "bad things". In that case, "bad things" are definite. What do you think?
"They hate themselves because they did bad things." Translation: Kendilerinden nefret ediyorlar çünkü kötü şeyler yaptılar.
"... kötü şeyler yapmıştılar"
"Kendilerinden nefret ediyorlar çünkü kötü şeyler yapmıştılar" -
They hate themselves because they have done bad things.
Your Turkish question which is different from Duo's has been given an English answer which is correct.
Yapmıştılar - "They have done." - "Something."
Yap - Do.
Yapmış - Done it.
Yapmıştı - (accusative) case. He/she/it - "Has done it."
Bebek kirli, annem onu yıkanmak yapmıştı. - The baby is dirty, my mother has bathed her.
Verdiğin cevap doğrudur. - The answer you have given is correct.
My written Turkish here is as spoken Turkish & is not 100% accurate as grammatically correct written Turkish.