Flies have infested my bedroom after holiday, please i'm begging someone help me?

spray the whole room in fly spray then shut the door and window. when the flies are all dead open the window and give the room a really good clean, take the rubbish out - double bag it if that helps, strip the bed, polish everything (after giving it a wipe down with a wet cloth) and give the place a really good hoover and it will be fine.