Hello Patrick,

This is the expected behavior at the moment wherein the requester's language is detected on the first request and it will be based on the selected language of the user from the Help Center. Please refer to this article: Adding multiple languages to Zendesk Support

As a workaround, may I suggest adding a custom dropdown ticket field in your forms, and having it prefilled when customers submit a request? With this field, you can create a business rule to change the requester's language based on the value of the field.

Let me provide the steps below:

1. create a dropdown field for the requester language and make sure that it's added to your ticket form.

2. Edit your theme's JS with this code:

 // Hide custom field
  $('.form-field.string.optional.request_custom_fields_23417384511385').hide();
  
    var htmllang = document.documentElement.lang;
  
  // Auto-populate English
  if (htmllang === "en-US") {
      $('#request_custom_fields_23417384511385').val('en-us');
  } 

  // Auto-populate German
 if (htmllang === "de") {
       $('#request_custom_fields_23417384511385').val('german');
  }
  
    // Auto-populate Spanish
 if (htmllang === "es") {
        $('#request_custom_fields_23417384511385').val('spanish');
  } 
  
      // Auto-populate French
 if (htmllang === "fr") {
        $('#request_custom_fields_23417384511385').val('french');
  }

This code should auto-populate the custom field while being hidden in the actual form.

3. Create a business rule/trigger to automatically set the "Requester's language" based on the value of the drop-down field.

I got the idea from this article here, remember to import the jQuery library as well as instructed here.