Q: "A man in white is singing his heart out." Does this mean that "A man is dancing his heart out."?
A: no

Q: "A man with a gas mask and goggles on his head." Does this mean that "A man is wearing a mask."?
A: yes

Q: "a young skateboarder on the sidewalk, next to a big tree" Does this mean that "A young skateboarder is outside."?
A: yes

Q: "They are riding a bike and talking at the same time." Does this mean that "The people have their feet on the bicycles' pedals."?
A:
yes