registration documents (Munich)

Hi everyone,

On the third of April I will start my job in Munich. I currently live in Belgium and will for the time being keep my oficial adress in Belgium. I have no official adress in Munich yet anyway and I'm on the hunt for a flat. The first weeks/months I might stay in a hostel.

I've got some questions however. My future employer asked me if I could provide her with the following documents when I arrive in München:

-Meldebescheinigung von deiner Krankenkasse
-Steuer-ID vom Finanzamt
-Sozialversicherungsnummer

My German is basic at best and specific words such as these are difficult to place. And it's all a bit confusing. Can I get these documents if i do not 'officially' live in Munich yet? If so, where exactly do I get them? Do these documents hace anything to do with the Meldebescheinigung? And can I get that document without an 'official' adress in München?

Thank you all for your help!