Translation:The man reads the newspaper on the cellphone.
"Nyhederne" is the Danish word "the news". Unlike in English, the word is countable. You can say "en nyhed" (one piece of news). By default, "Nyhederne" refers to "the news" in general, not any specific news.
I'm curious... since more and more people have only mobile phones now, is it getting more common to just use "telefonen" to refer to a mobile phone? Just like in English, "my phone" typically refers to the thing in your pocket now, not a device in your home?
Lack of consistency: it corrects me to "cellphone" rather than "cell", while in another exercise in this lesson "cell" was fine?
As på can also mean about, I translated it to ' the man reads the newspaper about the mobile phone'. Which to me makes sense as 'newspaper' suggests a hard copy