Practice for the viva, through a mock viva, a mini-viva, a meeting or even just a chat with friends, is essential: you have to build confidence that you can respond to questions. But even more important is building confidence that you have the ability to do well in the viva.
You don’t know what answers or responses you’ll need in the viva; you can’t know for certain what questions will be asked. But with confidence you can be certain that you can respond to every question that you’re asked.
You can do this.