The main thing in the examination are the physical phenomena and the basic principles and approximations that are used to understand them. There is no need to remember formulas except some simple and fundamental ones.
In an oral examination the teacher asks the student questions that are based on lecture material and exercises. A typical question about an exercise problem is "how would you start to calculate this?" Another typical question: "the matter xxx was considered in the lectures. Tell about it." In an oral examination it is easy to concentrate on essential things since often routine details can be skipped. However, also details of the calculations can be asked. The teacher gets fast an impression of the students knowledge since he can base questions on the previous answers. At the end of the examination the teacher gives feedback to the student. A grade is also given, but they are usually fixed only after several students have passed the examination.
Because of the corona epidemic, the oral examination is arranged on line. I recommend that you have camera on, but it is not a necessity. It is useful to have pen and paper close by so that you can write notes or do short calculations.
Please use Wednesday times if possible for you. Also prefer times adjacent to reserved times so that we can minimize breaks.