Young & Reckless - Moving to Berlin: HELP

Hallo, I am eighteen years old and am moving to Berlin soon. And just to note, I was in Berlin this past summer, and I fell in love with the city. This is not my first time moving or living abroad, however this will be my first time moving abroad on my own. Naturally I have many questions, and would greatly appreciate any tips or advice regarding the following!!

- I am planning on booking a shared flat via airbnb.com at least for the first couple of months! Is there a better way? I prefer this method starting off because the flat will already have furniture, amenities, WLAN, etc.

-This leads to the question of visas. Again, for the first couple of months I will probably be on a tourist visa, as I do not have a job offer yet. Can I still look for jobs on a tourist visa? I am going to Berlin and want to study German so that I may apply to university there once I pass the German qualification exam. Until then, I cannot apply to the school, therefore cannot be accepted, and hence cannot get a student visa. How does this work?

- Language schools. I am plan on studying linguistics, and I am a very fast learner when it comes to languages most of all. (I speak 6 going on 7) Is it worth taking a language course to learn? Could I learn what I need by living and associating in German?

- And what would be the best and cheapest way for transportation? I know that students usually have public transport passes provided by the school (Which is much cheaper than paying for a ticket EVERY time you have to go somewhere via ubahn and what have you). Is there something like this that I can look into??

- How many months should I plan on not having an income of some kind? If I go to Berlin with Protected content then perhaps I can survive for a couple of months? I'd like to set a goal for how many months it should take before I find a job there. This is crucial because if I don't find one, and I run out of money before then, I would have no choice but to leave. So, how many months would you guys recommend me having enough for??

Thank you in advance, I'm very excited to go to my new hometown!!
Tschüß