can a dataset be slicing into a result?

Try first method like:

IlanKatagoriGirdi.objects.filter(katagoriler='Girisimci Mentorlugu').first()

Or you can use slicing like this:

IlanKatagoriGirdi.objects.filter(katagoriler='Girisimci Mentorlugu')[:1]

This will not give error if the query returns no element