Are these good languages to learn?

Next year I'm going to be doing an arts course and I was thinking of doing a major in two different languages- Chinese(mandarin) and Arabic.

Is this a good idea? I remember reading somewhere that learning arabic is pointless because the dialects between countries varies so much that even learning the standard language tends to be useless. Is this true?

Also, would having knowledge of japanese help in learning chinese? I learnt Japanese throughout primary and highschool and was wondering if having knowledge of kanji could aid in learning chinese at all.

The university I plan on going to also offers Indonesian and Italian. Would either of those be worth learning at all?

If you plan on learning an Indo-European language I recommend you learn Esperanto first. Esperanto is the easiest complete language ever created and studies have shown that Esperanto learners learn Indo-European languages much quicker. Two languages for the price of 1.