He asked to describe favorite project and if you use any other their languages, such as React.Js they will ask you what you like about it. You can answer the technical questions in which ever language is fine. They aren't necessarily heard problems. But I have noticed that especially with facebook interviews, they aren't really trying to see how much you know, they want to see a little bit of that, but also how you work with the recruiters to building the answer.

1 Round of 4 question OA of easy/medium Leetcode questions 1 online technical interview of 2 easy/medium Leetcode questions, the first one is more standard of a question and the second one is a bit more open ended