Refugee help: Learning Arabic? How? Where to start?

Well, so first my situation because I feel it makes my motivation and my need clear. I'm a 16 year old girl from Munich in Germany. Right now I'm on a 10 months exchange in Japan learning Japanese. I will be back home around January. Since I'm politically interested I informed myself about refugees and what's going on for months (through mainstream German media, not deep into the subject outside of what happens inside Germany or affects Germany). Six months ago I decided I wanted to help as a volunteer in refugee camps in Munich. This was about two weeks before my exchange started, so I didn't have the chance to do it yet. These last six months the will to volunteer has been unbroken, especially since the situation in Munich has just gotten worse and help is needed. Now, that I've seen how much of an important role language plays in getting along with the people around you through my exchange, how much it helps you to be able to tell what you need to tell, I've decided to learn Arabic.

Not only because I want to help, but because I've been interested in it for some time. I have a rather long list with languages I want to learn, Arabic wasn't really high on the rank, but now I think I have a good reason to start learning it.

So, sorry for the long story, but now: What should I learn? There seem to be different dialects, so which is good to learn? Of course it would be great to learn one the majority of Arabic speaking people understand. How hard is it, where should I start at? Can I learn without a teacher? I think if I help I will get the chance to practice a bit, but is that enough? Of course learning the alphabet (?) should be one of the first things to do.

In general I'd just like to get some opinions on how to start. To be honest, since my exchange is not over yet and I'm still learning Japanese I won't start too soon. Probably from February on. But I do want to get some information on it, as it is quite an important thing for me.

Please keep in mind, I know about nothing. Complete beginner. Have no idea. Please be nice. (This text was written out of "I kinda have to start thinking about it" thoughts so it might be quite idiotic, I'm not sure)