"That is not how you speak to children."
Translation:ככה לא מדברים עם ילדים.
Indeed, Duo may not give a great translation. In any case, good to think about two main options for "meddabrim":
- "meddabrim eem mishehoo" [talking / speaking with someone]
- "meddabrim el mishehoo" [talking to someone]
As we already agree that we want to avoid the first, I'd opt for the second ... "אל ילדים"
Let me see if I can help So we have this: "That's not how you speak to children."
"ככה לא מדברים אל ילדים"
A good trick you could try to use in order to help make sense of the translation in a word-for-word-kind-of-way is to temporarily insert a word:
"ככה לא מדברים [אנשים] אל ילדים."
"That's not how people speak to children"
The tone in Hebrew is the sort that would be actually be best expressed as "[One / You] shouldn't talk to children like that [!]"
Well, כמה means "how much", so that is definitely not the correct answer. If that was a typo (and you meant ככה) and your question was about זה, keep in mind that not every "it/this/that" in English translates to זה in Hebrew. In a sentence like this, זה would not be used.
I actually think it's correct. Negating a verb, the לא has to come in front of it, as you say, but we don't have to negate the verb... ככה לא מדברים לילדים has the structure (not talk)(like that), לא ככה מדברים לילדים has the structure (talk)(not like that), and I think both correspond equally well to the given English sentence (which has a different structure anyway). I also think both orders sound natural (although ככה לא מדברים maybe just a little bit more likely).