Generally the first phone interview is talk about your background, what project and tech stack you used, and he introduced OfferUp's development and other thing etc. Not difficult and just to tell yourself.
Phone video Interview: The interviewer seems forgot this schedule, I send him message notify him. During this process, interviewer looks has no interest of me, tell sth about OfferUp, and ask some question about your project on resume, but I didn't prepare it well, and performed bad.
The coding part, he gave a simple array algorithm question, I just ask one question then start work on it. I think you should chat more details with him. Before I finish my code, interviewer start to check if bug exists, I really don't like that. You'd better tell him I will check my code myself, after I am done, I will tell you. Both parts I didn't perform well, this is my first interview and finally I didn't get onsite interview. Hope it will better next time.