Translation:I will talk on a cell phone.
Duolingo (as a teaching tool) has to strike a balance between natural translations and technically correct ones, and it leans heavily towards the latter. You need to be careful you're not adding or omitting information (e.g. dropping the 'cell' part)
Tenses are trickier because Duo wants to make sure you recognise the tense in the original language, often by expecting you to use the equivalent in the target language. So in this case you need to use the present simple because that's the same as the original, others are present continuous so you need to translate to that
This can make for some awkward and stilted translations (like in English we'd say "I am talking on a cell phone" instead of "I talk"), but that's their way of ensuring you understand correctly. You just have to answer in the way they expect, you get used to it!
It's a good idea to try not translating everything so literally and directly. Some words have more "wiggle room" to them repectively in either language. Thats why when you read subtitles, they often find a different way to say the same thing, rather than literally printing out a word for word translation. 話 can mean story. 話 can mean speaking. This doesn't mean one is better than the other, or that there aren't other words in Japanese that also mean story, such as 物語. I also notice people tend to dismiss words too easily as "old" just because there is a newer word for it, when i hear the "old" word every day here in Japan.
trust me... only referring to mobile phones as cells phones is like the last thing that the dev team needs to adjust. there are so many problems with this course.
It is still better than Memrise for everything besides vocabulary, but they really should follow suit with them and provide literal translations. (i am using the app i assume web is the same).
or mb even just having a page of text discussing new grammar elements that will be introduced in each block of study
from my understanding of "on the phone" (meaning that someone is using a telephone) vs. "over the phone" (meaning that something is done using the phone as a way to do it), can で here be translated into "over"? I speak (about something or to someone) over the cell phone instead of I speak on the cell phone.