Open the app settings → Navigation section → Voice instructions. Here you can choose a language and turn off voice instructions. For now, voice instructions are only available for car and bike routes.
Note: we don’t use pre-recorded voices but TTS (text-to-speech) engine. It means that the voice output quality and language availability depends on the TTS engine installed on your device.
If you are an Android user and the option is disabled, please check system TTS settings.