null value in column "name" of relation "contact_contact" violates not-null constraint

DETAIL: Failing row contains (9, null, miarisoa00@yahoo.de, , null).

IntegrityError at /contact/contact/
null value in column "name" of relation "contact_contact" violates not-null constraint
DETAIL:  Failing row contains (9, null, miarisoa00@yahoo.de, , null).
Request Method:	POST
Request URL:	http://127.0.0.1:8000/contact/contact/
Django Version:	3.2.15
Exception Type:	IntegrityError
Exception Value:	
null value in column "name" of relation "contact_contact" violates not-null constraint
DETAIL:  Failing row contains (9, null, miarisoa00@yahoo.de, , null).
Exception Location:	D:\MKSD_SITE\MKSD_WEB\site\lib\site-packages\django\db\backends\utils.py, line 84, in _execute
Python Executable:	D:\MKSD_SITE\MKSD_WEB\site\Scripts\python.exe
Python Version:	3.9.13
Python Path:	
['D:\\MKSD_SITE\\MKSD_WEB\\site\\src',
 'C:\\Program Files\\Python39\\python39.zip',
 'C:\\Program Files\\Python39\\DLLs',
 'C:\\Program Files\\Python39\\lib',
 'C:\\Program Files\\Python39',
 'D:\\MKSD_SITE\\MKSD_WEB\\site',
 'D:\\MKSD_SITE\\MKSD_WEB\\site\\lib\\site-packages']
Server time:	Sun, 04 Jun 2023 16:39:42 +0000

views.py

def Kontact(request):

	if request.method == 'POST':
		contact = Contact()
		message_name 	= request.POST.get('message-name')
		from_email 		= request.POST.get('from-email')
		ville 			= request.POST.get('ville')
		message 		= request.POST.get('message')

		contact.name = message_name 
		contact.email = from_email
		ville 			= ville
		contact.subject = message  

		contact.save()

		message = f"""  

		Name: {message_name}
		From: {from_email}
		Stadt: {ville}

		New message: \n\n{message}

		"""

		# Send email
		send_mail(
			message_name, #subject
			message, #message
			from_email, #from email
			['kontakt.mksd@gmail.com'], #to email
			fail_silently=False, 

			)


		return render(request, 'contact.html', {'message_name': message_name})

	else:
		return render(request, 'contact.html', {})

models.py

class Contact(models.Model):
	name = models.CharField(max_length=50)
	email = models.EmailField(max_length=50)
	ville = models.CharField(max_length=100)
	subject = models.TextField(max_length=355)

	def __str__(self):
		return self.name

Template - HTML

<div class="row">
	<form method="post" class="was-validated">
		{% csrf_token %}

		<div class="col-lg-6">Email (erforderlich):
			<input type="email" name="from-email" class="form-control mb-30" placeholder="Your Email" required>
		</div>

		<div class="col-lg-6">Phone
			<input type="phone" name="phone" class="form-control mb-30" placeholder="yours">
		</div>	

		<div class="col-lg-6">Name (erforderlich):
			<input type="name" name="name" class="form-control mb-30" placeholder="Name" required>
		</div>

		<div class="col-lg-6">Stadt
			<input type="stadt" name="stadt" class="form-control mb-30" placeholder=" City">
		</div>									

		<br><br><br>
		<div class="col-12">
			<textarea name="text" class="form-control mb-30" placeholder="text">
			</textarea>
		</div>
		
		<div class="col-12 my-3">
			<button type="submit" class="btn btn-success">
				Send
			</button>
		</div>

	</form>
</div>

The name of the input element is name, not message-name, the same with ville which is stadt and message which is text in your HTML form, so you use:

<pre><code># views.py:
def kontakt(request):
if request.method == 'POST':
message_name = request.POST[<b>'name'</b>]
from_email = request.POST['from-email']
ville = request.POST[<b>'stadt'</b>]
message = request.POST[<b>'text'</b>]
Contact.objects.create(
name=message_name, email=from_email, ville=ville, subject=message
)
message = f&quot;&quot;&quot;

    Name: {message_name}
    From: {from_email}
    Stadt: {ville}

    New message: \n\n{message}

    """

    # Send email
    send_mail(
        message_name,  # subject
        message,  # message
        from_email,  # from email
        ['kontakt.mksd@gmail.com'],  # to email
        fail_silently=False,
    )
    return redirect('<em>name-of-some-view</em>')

else:
    return render(request, 'contact.html', {})</code></pre>

It is often a bad idea to use multiple (natural) languages concurrently. You seem to partly English, German and French, making it all very confusing.

> Note: Please use request.POST['ville'] over request.POST.get('ville'). Using <code>.get(&hellip;)</code> often only silences the error, but not the problem: indeed it will work if the key is missing. But if the value for that key is really required, it will only result in more trouble later in the process.

> Note: It is better to use a Form&nbsp;^[Django-doc]
> than to perform manual validation and cleaning of the data. A Form will not
> only simplify rendering a form in HTML, but it also makes it more convenient
> to validate the input, and clean the data to a more convenient type.

> Note: In case of a successful POST request, you should make a redirect
> ^[Django-doc]
> to implement the Post/Redirect/Get pattern&nbsp;^[wiki].
> This avoids that you make the same POST request when the user refreshes the
> browser.