Are there many advertisements in your country?
Definitely, there are. They appear all over the place from the streets to social
media with a high density. For example, there is a multitude
of colorful flyers sticked on the street walls in Sydney.
All over the place (expression) everywhere
Density (n) the quantity of people or things in a given area or space.
A multitude of (expression) a very large number of people or things
Flyers (n) a small handbill advertising an event or product