The Private Multi exam and checkride is very different from the single engine checkride as it is considered an “add on” checkride. Assuming that you already have a single engine license, the private multi is just “adding” multi engine privileges to your existing certificate. With this in mind the multi checkride focuses only on the areas relevant to multi engine airplanes.
The oral exam for the private multi will consist mainly of questions relating to two engine airplanes amd to the airplane that you are flying for the checkride. Questions will typically be things along the lines of “Tell me about the four aerodynamic factors that are unique to multi engine airplanes”. I would not expect more basic questions such as “Describe the types os airspace”. As a private pilot already you have already been tested on that information.
That being said, anytime you are with the FAA anything is fair game so it is best to stay up to date on all of the information that is out there.