Magyar (Hungarian) does not resemble any other language I've ever learned. Most of the time I can usually decipher some words based on my knowledge of other languages. Not this time. The most closely related languages are Mansi and Khanty of western Siberia. Silly me for never having learned those! The only word that was at all familiar was Hello...which means goodbye. The Magyar alphabet has 39 letters; 14 of which are vowels. Nouns can have up to 18 cases (this number varies from different sources as you'll see below). Having learned English in an American public school, I have no idea what a noun case is or how many there are in English! Word order in sentences is free. So you can say, "I'm eating an apple," or, "I'm an apple eating," or, "An apple I am eating," or "Eating an apple I am..." you get the point. According to our walking-tour guide, Yoda's lines in Star Wars were translated from English to Magyar and then back to English resulting in the odd word order.
Consequently, learning even a few key words proved difficult. I got please and thank you and that's where it ended. I got confused every time I went to leave a place and someone said, "Hello!" Still, it was always nice to see a shop owner's or waiter's face break into a smile after saying, "köszönöm (thank you);" and that's the real reason for doing it. Especially after you just gave them a dumb-founded blank stare when they told you the price, usually resulting in them showing you the number on the register. Even words that are usually really easy to pick up while traveling like, "Egészségédre! (Cheers!)," (heard any time you go to a pub or bar) look impossible in Magyar. Thankfully, many Hungarians speak English...at least in Budapest. But when they didn't there was absolutely no chance I was going to understand anything they were saying!
A quick Google search for difficult languages has Hungarian at #4:
4) Hungarian: First of all, Hungarian has 35 cases or noun forms. That fact alone makes it a candidate in this list. Hungarian is full of very expressive, idiomatic words, and suffixes. The high amount of vowels and their deep-in-the throat sound makes it very hard to speak as well. It takes more effort to learn it and maintain what you learned then most other languages.Other lists had it at #2 or #9. Of course, it depends on what your native language is and your overall language-learning ability. Despite it being the most widely spoken non-Indo-European language in Europe, I don't see myself making a study of it!