Previously
There are lots of questions you could be asked at your viva, including questions you’ve never been asked before! But by the time you get there you will have had lots of practise responding to questions, certainly enough to do well with your examiners.
There’s a lot of pressure on the whole situation, but you have experience with that sort of thing.
You can’t be sure what your examiners will ask, but before the day of the viva you can find out more about your examiners and rehearse for being in the viva. You can’t arrive perfect but you can take the time to get ready.
Yes, there’s a lot you won’t know about before the moments of your viva, but prior to arriving there you can do as much as possible to be ready for the situation.