If your research wasn’t complicated then it probably wouldn’t be up to the standard needed for a PhD. It will help you, however, to explore how you can express your ideas clearly, simply.
The process for getting ready for the viva isn’t a straight-forward linear process; deciding when to start and what to do can be a complicated business. You can simplify things by asking simple questions and doing simple things.
Knowing what to expect from your viva is a very complicated question. It depends on what field you’re in, what university you’re at, whether your viva is in-person or over-video, who your examiners are, what time of year you submit and many other factors. Or simply, you can expect a conversation for several hours or so, lead by examiners and their questions.
Ask anything about the viva and the honest first response is: “It’s complicated.” If you find the right help and explore a little though, you’ll probably find that there are simple things to consider which will really help you.