Arabic is considered difficult for several reasons, some of which are:
1- Characters used are different from Latin Characters
2- Unlike English, you might feel yourself reading things backward. It's similar to French in this matter. What I mean to say is that instead of saying, for Example; "Jordan Hotel" you will say "Hotel Jordan". Remember this rule
3- Numbers are also different as we use "Hindi" numbers. Again remember the rule in (3) above, numbers are read "One Twenty" instead of "Twenty One"
4- Punctuation (I mean here the Signs above or below the letters) are tricky.and you need to master them as they might alter the meaning of the word. I don't mean to make it more difficult but look at it this way. An example; the first letter in Arabic is similar to the English "A" and called Alef. This single letter, when written without proper punctuation can mean;
   i) the letter "A",
   ii) One Thousand
  iii) Got used to
  iV) similar to (wrote) in " I wrote a book"
5- Many times, especially in the spoken Arabic, one word may have different meanings, depending on the context. You need to remember that. We do joke about that fact. Remember the word (Tayyeb) it has hell of meanings and can differ from OK or nice to I will kill you (LOL)
6- Grammar is difficult but people are quite forgiving when it comes to Grammar as they realize how difficult it is even for Arabs themselves. Mostly they won't comment and they shall be happy to know that you can speak and understand Arabic.
Remember one thing, once you master Arabic then there's nothing you can't learn (lol)