https://www.youtube.com/watch?v=1wEtsGldrkc

I think the hardest is Arabic

are many dialects in Saudi Arabia

to have five different accents

and often difficult to understand what they say

The one you can't practice often enough. 

Everything else gets easier, sooner or later.

in fact i think french is not very difficult .Arabic is widely accepted the most difficult language in the world, and the second is chinese  :)  by the way, i like a brazilian football player since i was in middle school, kaka  lol

I think that Chinese, Japanese and Korean are more difficult than French