Totally 2 rounds, The first is about 3 hours and is very detailed, mainly asking about past research projects and experiences, you have to know your project very well. The second round is also about research experience but is more general.

Very calm, asked questions on the fundamentals, questions about the projects I had done. Very encouraging, and helpful if you got stuck on anything. Knowledgable about the subject. Informal, because of the covid setup I suppose.