Translation:They are carrying the thing somewhere else.
the english sentence "they carry the thing elsewhere" is only grammatically correct if it is used in a way that implies that they repeatedly carry the thing elsewhere. "(on sundays,) they carry the thing elsewhere." or "they (always) carry the thing elsewhere." or: what do they do with the thing? they carry the thing elsewhere.
so this form of a sentence would need the indeterminate verb in czech, which is "nosit," in the infinitive.
the sentence we have here is "they are carrying the thing elsewhere," as in, at this moment they are carrying the thing elsewhere. there's no indication that they regularly carry the thing elsewhere. this could be the only time. so we use "nést," which conjugates to "nesou" when used for oni.
hopefully that is understandable and technically correct......
I am native AmE. Strictly in terms of grammar -- by which I mean the creation of a valid sentence --"They carry the thing elsewhere" is a valid sentence, since it has a subject, verb, object and adverb all in their proper places
However, in terms of usability, it is not appropriate here. Without some additional qualifying information it feels like an incomplete thought.
Please also read earlier comments on the use of the verbs nést and nosit, since they are relevant to the current action/repeated action issue.
Using "are carrying" to denote an action in progress is the appropriate choice in this exercise.
"What do they do?" "They carry the piano upstairs." "Why? It was a perfect location." "The boss ordered so. They take everything out of this room and put it upstairs."
So, is that dialog unnatural to a native English speaker? Does it really have to be in the present continuous tense?
Yes, exactly. It already starts with the question words "kde?" and "kam?"
Note that "tam" and "všude" play two roles.
English has archaic words for direction:
- where? - here, there
- whither? (= where to) - hither, thither
- whence? (= where from) - hence, thence