What does it mean to turn over serfs and sing?

This sentence means that once oppressed slaves or people at the bottom of society, after being liberated or turned over, express their joy and gratitude and sing their favorite songs.

Freedom and liberation are one of the most basic needs of human beings. Only when freedom and liberation are realized can people really enjoy life and pursue happiness.

It also expresses the desire for freedom and resistance to oppression, inspiring people to fight for freedom.