With my son in Berlin- Where to start?

Hello to all expats!
My son is going to do his study in Berlin ballet school. I need to come there with him, because he is still young.
We are EU citizens, but reading all the rules I get confused about it. What is most important to do when we arrive- registrations, rents(recommend me company and cheap rental places), medicals insurance, Where?
We need to learn German also- what about German lessons? Where?
Most important for me is about working permit for me?

What about driving license, pets walking- Help please!!!!

Thank you in advance!