You're right, but Duolingo doesn't allow us to use two stresses in the best translation.
We have added το όνομά μου as alternative ;)
In general, there are no Greek word with stress beyond the THIRD syllable. So the stress in these cases is double, as όνομα μου is pronounced as one word actually, όνομαμου. That's why it is used double stress. So in any case you have to stress beyond the third syllable, put an accent on the second syllable, starting from the end. So it becomes όνομά μου. Is it clear enough?
I was wondering about "Duolingo doesn't allow us to use two stresses in the best translation.", not the secondary stress itself ;). Still, someone will surely find your explanation helpful.
"Are there no commas after όχι resp. ναι in Greek?" - Interesting question. And the answer?
When clicked on individually, Duo linguo translated nearly every word in this sentence as a form of "not". I'm very confused...
It's just a multi-part hint that's added to make the translation of the sentence easier. There are also individual hints for each word, at the bottom of the list. ^.^
Just a question, is the sentence (δεν είναι το μου όνομα) . Grammatically correct? Or does it have to be as it is on the exercise?