Congrats! I interviewed the 1st round. It took around 1h, including some resume questions and mainly technical questions (math, finance, computer science, statistics, machine learning, and economics, all possible!). From my own experience and some research, technical questions are very dependent on your interviewer’s background and your previous experiences. For example, my interviewer asked what programming language I am most proficient in and then asked questions about it. She also asked a macro economics question because that’s related to her daily work.
I’d suggest looking at your interviewer’s LinkedIn profile to guess some directions. For technicals, first fully understand every technical terms on your resume and make sure you can answer related questions. Green book can be a good resource if you get time.
Interviewers are very nice, and they are willing to help if you get stuck. Be confident and best of luck!