The difficulty depends very much on the type of your own language. For example as a speaker of Finnish I wouldn't consider Turkish hard at all because of agglutinative morphological technique (affixes are glued to root element of word).
Case systems in Finno-Ugric languages are notoriously difficult, but are they harder than learning all uses of prepositions? And grammatical gender and articles, on my point of view they are hard, because Finnish doesn't have them.
I understand what your saying but this list (as it says in the description of the quiz) is based on English speakers. I also get that even for English speakers some of the languages wouldn't be as hard as others to learn but i didn't write the list so yeah! :)
Case systems in Finno-Ugric languages are notoriously difficult, but are they harder than learning all uses of prepositions? And grammatical gender and articles, on my point of view they are hard, because Finnish doesn't have them.
I am very surprised that Icelandic is considered so difficult. It is very archaic compared to English, but still, they are both Germanic languages!