There was a research that showed that the 3 most difficult languages in the world are Hungarian, Dutch and Bulgarian, then it comes polish one. And no, I don't have problems with Bulgarian.
Well, I wish to see that research - it must be a revolutionary one. I guess it refers only to European languages but still there are other languages that are much more difficult - like Basque, Suomi, Albanian and many more. I'm a linguist and I must say that statements like yours above are pure speculation and are very subjective, so my advice to you is to think more before writing serious things like that.
BTW, I was just wondering - where are you coaching?