"If you believe me then I will help you" still marked wrong, should be accepted.
I do agree with you & Duo can be fickle.
Your inclusion of, "then" in the English answer may be why it was declined by Duo. Your answer should have been accepted.
Then --> "O zaman."
"Bana inanırsan (o zaman) sana yardım ederim."
You can now see why such a minor change in the English answer needs to reflect the Turkish question to it.
You have created a new English question & Turkish answer though.
Very sorry & thank you.
sorry to be trouble but i am seeing the aorist tense used predominantly and was wondering why? i thought it was habitual or meaning time was not important, but is it just duolingos examples- focusing on the conditional 'if' or does it normally come with aorist generally?