Translation:The dog is not running to the policeman, but to the students.
What? Is this a joke? I wrote "The dog is not running to the police officer, but to the students" and it marked it as wrong! Please, make up your mind as to accepting both simple present tense and present progressive when there are not explicit clues on using just one of the two, or...is it because of the police officer and not the policeman? I remember I had to rule out the use of "policeman" from previous lessons because it was not accepted.
Okay okay we already get the structure of 'nem xxx hanem xxx'. It feels like the whole course is full of these sentences, the proportion does not correspond with the real life usage, which gets annoying and boring after some time. It just adds length to the sentence with no learning value. I suggest something more creative like "I want to go the movies today, but my girlfriend is sick" - see you use "but" but in a different way.