Can you write "They are hearing the children"? Maybe that doesn't make sense in english? English is not my native so idk...
Yes, you can. It sounds a little odd, i can't quite explain why, but there are contexts where it would sound right. Same with seeing. Hearing and seeing are more passive, like a state you are in, compared to listening or watching, which are actions.
Tj1983, you're right that that the verbs 'hear' and 'see,' like 'perceive' or 'know' are more like a mental state, they don't indicate a process. You either see / hear / perceive / know something or you don't, though to indicate coming to that state you could preface them with 'begin to,' or 'get to' for 'know,' as in the song, 'Getting to know you.' This is why it seems odd. Such verbs are not usually put into a progressive (UK /continuous) tense (be doing, etc.), although McD grabs our attention by deliberately using it: I'm loving it -- perhaps to change English forever. :-)
Could "They are hearing children." also be a correct translation? It said that I was wrong.
We decided that using "hearing" in Present Continuous is really rarely correct and without some specific context we don't accept it.
I agree with your assessment. In fact, one illustration of the out of the ordinary use of the present progressive (/continuous) for such verbs as hear or see would be that if I heard someone say 'I'm hearing (/seeing) things,' I would presume that meant perceiving things that are not objectively there. As another illustration, try moving such use to another parallel tense. Although one would say 'Did you hear that?', I would never say 'Were you hearing that?' The verbs 'hear' and 'see' have to do with auditory or visual perception having taken place at a least some moment or other, whereas the verbs 'listen,' 'look,' and 'watch' require at least a minimally prolonged period of attention.