Drag Drop Upload don’t work

Hi Mr. Mongaya,
my problem is, that the drag drop upload is not shown in my contact form.
With another theme it works perfekt.
What is to change/add at my theme?

Who can help and answer my question.

Here is the code of the form:
<label> Dein Name (Pflichtfeld)
[text* your-name] </label>

<label> Deine E-Mail-Adresse (Pflichtfeld)
[email* your-email] </label>

<label> Betreff
[text your-subject] </label>

<label> Deine Nachricht
[textarea your-message] </label>

[mfile upload-file-509 limit:5242880 filetypes:jpeg|pdf|gif|jpg max-file:10 id:xy class:xy]

[submit “Senden”]

Kind regards
Tanja

The page I need help with: [log in to see the link]