Have / did

Hi



I am studying for my English grammar exam (I am studying English at university).



To prepare for this exam I am doing these old mock exams and one of the questions on these exams are:

Comment on the following sentences produced by Danes (I am Danish by the way).



So the sentence that I am having trouble with is:

I haven't slept very well last night.



My guess is that the sentence should be: I did not sleep very well last night.



But the problem is that I have no idea why it should be did and not have, and if that is even the case.





Just to make something clear: this is not my actual exam. The reason why I am asking for help is that I would like to a qualified guess to what a comment on that sentence could be like. Since I have no idea and if I got that question at the exam I would be totally lost.



Oh yeah, I am new at this place/forum so I have no idea if posted this question at the right place.



Thanks