What do you think about the idea of ​​8 billion people living in a city the size of britain?

https://www.youtube.com/watch?v=VKkQWIMR0ng

This is a South Korean YouTube video that assumes what it would be like if 8 billion people lived in a megacity of about 240,000 square kilometers.

However, they think it's easy to make that assumption because despite South Korea is a very dense country and its high urban population density (Seoul, for example, has a net urban population density of 30,000 people per square kilometer, excluding mountains and rivers), it's a very uncrowded.

I wonder what it would be like to live in a megacity like that from a foreigner's perspective.