It can be pretty easy depending on your circumstances. Everyone is going to have a different response for you. Here are my responses:
1) Go to
KVR at
Poccistraße.
2) Bring:
- apartment rental contract
- proof of health insurance (must be valid in DE)
- bank statement showing that you have money in the bank
- proof of income (showing that you have a regular income stream)
3) Bring about €50 for fees (I think it was about €35 last summer)
From reading all the various posts on this topic, it is much easier to do if you can be characterized as a "freelancer" (i.e., self-employed) so you are not taking a job away from someone else. This is easier to establish for professions like doctors, lawyers and the like. I think NOFXMike was able to do this as a tour guide, if I recall correctly from his previous posts.
Another possible way is for your German girlfriend to sign a Verpflichtungserklärung, declaring that she will take financial responsibility for you during your stay. She will need to bring: proof of income, apartment rental contract showing the size of the apartment (i.e., sufficient for 2 people), proof that she has paid at least two months rent for said apartment and proof that you have health insurance.
That is how I got a residency permit for my US girlfriend, even though I am a US citizen too.
Good luck.