> top 5 in the world

By what measure?

https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nomi...

> Our city is the richest in our country, which is at the top 5 in the world

Right, so you're saying the country itself is within the top 5 by GDP not that the city within your country is a top 5 city (regardless of country).

Yes, they're saying it's the richest city in their country, which is in the top 5 [richest countries] globally.