I dreamed of knocking gong, which was so big that it was blown away by the wind and crushed by a car.

Don't care too much. There are two possibilities for dreaming. First, you think about it every day and dream at night. Second, you don't sleep well. Try some foods that help you sleep. Third, don't be superstitious. Don't believe what happened in your dreams. It's just a joke from God. Keep an optimistic and positive attitude and wish you a happy day.