Perfect answers don’t exist in the viva. With preparation and rehearsal you can give good responses.
A perfect thesis is an ideal: if you’re very fortunate then perhaps you’ll pass your viva with no corrections required. It’s something you can only hope for though.
Vivas have ranges of expectations and patterns of experience. You might have an idea of your perfect viva. You can’t really steer your viva towards the 90-minute, no-corrections, easy-conversation that you might have in mind.
Perfects and ideals are nice, but you’ll over-commit your time, energy and focus if you chase them.
Instead, just do the work you can. Do your best research, write the best thesis you can, prepare with the time you have – while resting and looking after yourself and your other responsibilities – and then show up on the day of your viva determined to engage with your examiners.
Your best is better than chasing PhD perfection.