Please boost. A dear friend of mine wants to move to Germany ASAP and we can use all the help we can get.

How does a language learning visa actually work?
How does one prove financial stability to the government? Especially, in case my income doesn’t suffice to take financial responsibility for her, where do we get the money for the locked bank account option?
Which organizations can help us get more information and answer questions? The official government websites give a good overview but lack depth in critical aspects.
Have you moved from the US to Germany or know someone who did? How did that go? What unexpected things did you encounter that we should be aware of?

Anything helps. Please dump all leads and ideas into the replies. And boost this far and wide. ETA (estimated time until her arrival in Germany) is 3 weeks from the time I’m posting this. She can come to Germany and stay for 90 days without a visa. Until then, she needs all the paperwork to be done and over with and her visa approved. Please boost this! It’s kinda urgent.