Continuing school in Germany

Using a throwaway because my friends know about my main.

So, let me start by giving a few info. Next year I will be attending my 10th year in one of the [DAS school](https://www.auslandsschulwesen.de/Webs/ZfA/DE/Schulnetz/DAS/das_node.html). So, the language is not a problem, and the curriculum shouldn’t be too different to what I have here. My brother also lives there, and to my limited knowledge, he should be getting his german citizenship soon. He assured me that he will offer help and support.

So my question, is something like this even possible? I already know about boarding schools, but the price ranges I looked at are extremely unreasonable for me(at least 30k euros per year).

My plan is to rent a flat/room . I wasn’t able to find a lot of information on this, but it seems like it’s possible to do as a 16 year old, but I need to have the permission of my guardian. Please correct me on this. Also, will my brother be automatically my guardian after declaring a Verpflichtungserklärung? How would I go about this one?

To finance my stay, I will be working part time, and my brothers will also help me. So the finances should be no problem, if anything they will be much lower than the fees I pay here for my school.

Last question: what will be the needed papers for schools to accept me? Can they accept me without being physically there? Is it like universities where they will accept me, and I will take the paper of admission and submit it for the student visa?

Vielen Dank!