Translation of "everyone knows" into Spanish

This is the problem when everyone knows your business.

Ese es el problema cuando todo el mundo conoce tus asuntos.

As everyone knows, air is a mixture of gases.

Como todo el mundo sabe, el aire es una mezcla de gases.

Everyone knows everyone else.

Todos conocen a todos.

Nearly everyone knows that my mother tongue is Turkish.

Casi todos saben que mi lengua materna es el turco.