Can I use build-in intents in german?

I am looking for an easy solution to launching feature of my app through the "App Action" feature of Google Assistant.

I found info about built-in intents such as actions.intent.OPEN_APP_FEATURE, but locale is limited to English. Does this mean it only support English utterance? If it is only supports English, can you help me how to use it using German?

As documented here, the actions.intent.OPEN_APP_FEATURE is currently only available in the following locales:

• en-US
• en-GB
• en-CA
• en-IN
• en-BE
• en-SG
• en-AU

If the locale you want isn't supported - there isn't anything you can do, really. You can try creating a conversational action that will, at some point in the conversation, offer a link that will trigger your app, but this works outside the App Action framework.