It’s your responsibility to do your research; your responsibility to prepare for the viva; your responsibility to engage with your examiners and pass the viva.
But look around: there are lots and lots of people who can support you. They can’t do the work, they can’t do your prep, they can’t answer the questions on the day. They can do a lot to help you through it.
Ask your community for help. Ask colleagues for advice and their time. Ask family for help to give you the space you need. Ask your supervisor for feedback and insight. Ask your institution for help with understanding the regulations and expectations for your viva.
You have to do a lot to get through a PhD, but you don’t have to do it all alone.