My interview experience:
This forum helped me a lot and I think sharing my experience may help other ppl. Thanks to everyone, especially Simon.
My case has been approved today. Right after my interview, and my status changed to "new card is being produced". I had no bio appointment and they recorded everything right before the interview, do not worry if you have no bio appointment.
My interview was at 7;15 AM. They opened the door right at 7 AM and everyone went to a security check, just like airports. Then my officer called me and started talking. There was a little document shortage, I am currently on an F1 visa and the officer hadn't my I20, I am sure that I put it into my package though. It is better to have a copy of everything with you while you go to the interview.
After the oath, he asked about my job, I am a research assistant as a Ph.D. student and the officer did not know what does that mean, I explained and he got cleared. Then he read the I-485 questions one after the other, but not all of the questions, and I answered in the shortest and the most direct way. Then he said I'm gonna approve your case today and you will receive your GC in a week.
Note: My officer thought I am on an OPT, make sure your officer knows the nature of your job if you are a research assistant during your Ph.D. study. I needed to explain that it is an on-campus job and you cannot work outside of the University, and also you obtain credit by working in the lab just like the way you obtain credit in coursework.
The interview is really easy, do not worry! they are nice and understanding.
Wish you all the best.