Translation:They believe that they know you, but they do not.
I'm honestly surprised that the second part of the sentence uses the verb 'å gjøre' rather than 'å kjenne' - This sounds like such an anglicism. "they believe they know you, but they don't (know you)" The 'don't' in this sentence is the auxiliary 'do', as in "I like/I DO like/ I am liking", which I thought Norwegian, and every other language I've studied, does not have in the present tense...
Not inconsistent, you're just comparing apples to oranges. :)
-"Man gjør ikke det." is a standalone sentence in the course.
-"...de gjør ikke det" is but a part of a whole, and the rest of the sentence enables the different translation. "...they do not do that" is among the accepted translations for this sentence.
I dont know about you guys but i just started this subject and this was an exercise in which you would listen and drag the words into the lines in the correct order to complete the exercise but for me the exercise was already done... I just had to click the button to confirm. What the heck is happening i feel like the app is getting more broken each day that passes. I have screenshot to confirm though im lazy to post it online and link it here