Signup-Form embed code not correct

Signup-Form embed code not correct

I am having problems with creating the embed code for the signup-form. It looks as desired when I click "Preview" but when I copy and paste the HTML-code, the signup-form is wrong.

For example: I did change the "Display Field Name" here:
Mailing Lists  ->   My List  ->  +Signup-Form  ->  Edit Form Fields
 (I need the form for a German website so I translated the display field names.)

It seems to work just fine when I hit "Preview" but in the HTML-code all the display field names change back to their English original.

I also added custom fields with a default value. The default value in the form field shows up in Preview but disappears in the HTML code.

What's wrong?