Subject + 当 + Role/Position
The verb 当 (dāng) means "to serve as," "to act as," or "to work as," indicating the role or position someone holds. It is followed by the role or position noun. For example, 当了十年的警察 means "served as a police officer for ten years."
她大学毕业后当了一名老师。
Tā dàxué bìyè hòu dāng le yī míng lǎoshī.
After graduating from college, she became a teacher.
他当了三年的志愿者。
Tā dāng le sān nián de zhìyuànzhě.
He served as a volunteer for three years.
谁愿意当这个项目的负责人?
Shéi yuànyì dāng zhège xiàngmù de fùzérén?
Who is willing to be the person in charge of this project?