2 sentences

1. 他响应号召去下乡，后来政策变了，他才回城。

   tā xiǎng​yìng hào​zhào qù xià​xiāng, hòu​lái zhèng​cè biàn le, tā cái huí​chéng.

   He responded to the call to go to the countryside, and only returned to the city later when the policy changed.

   Source: Dong Chinese Dictionary

2. 他在农村当了五年的知识青年，后来才回城。

   tā zài nóng​cūn dāng le wǔ nián de zhī​shi​qīng​nián, hòu​lái cái huí​chéng.

   He spent five years as an educated youth in the countryside before returning to the city.

   Source: Dong Chinese Dictionary