Invoke Assistant on your headphones. (For Pixel Buds, touch and hold right earbud.) Tell Assistant to help you interpret a language. (Example: “Help me interpret French.”) This will launch Google Translate in conversation mode with your languages set.
Activate your headphone’s mic. (On Pixel Buds, touch and hold the right earbud.) Start speaking in the language listed under the headset icon. Deactivate your headphone’s mic. (On Pixel Buds, release finger from the right earbud). The app on your phone will then translate what you said in your selected language.
Hold your finger on the mic icon in your Google Translate app. Have the other person respond in the language listed under the mic icon. When they’re done, release your finger from the mic icon. Their response will be translated and played back via your headphones.