Hm, in my field of study, there are not many of these particular case studies out there, so yes, it was a coincidence and I would not have looked in the city my partner lived in if he would not live there. Of course I don't know that CBP WILL allow me into the country for such a long time. I am planning on bringing proof of my studies in Germany, my part time job with a letter from my job, my apartment lease etc. I am fully aware that I don't have any rights with ESTA. And no, I am not working on ESTA, that would be a paid job. I have done some research online and as far as I can tell, independent research is okay under ESTA. Also US universities recommend it for independent research of foreign students. However, if anyone here has done a similar thing and has further insight, I highly appreciate it