Previously you learned that 謙虛 (qiānxū) means modest, self-effacing, or humble. Earlier you also learned that 誠懇 (chéngkěn) is sincere, true-hearted, or whole-hearted.
So taking 謙 (qiān) from 謙虛 (qiānxū) and 誠 (chéng) from 誠懇 (chéngkěn), 謙誠 (qiānchéng) means modest and sincere.
Let’s review these together:
You are modest: 你很謙虛 (Nǐ hěn qiānxū)
You are sincere: 你很誠懇 (Nǐ hěn chéngkěn)
You are modest and sincere: 你很謙誠 (Nǐ hěn qiānchéng)
Example: Joe never gloats and is always honest. I like to tell him, 你很謙誠 (Nǐ hěn qiānchéng).