i created a couple of modelforms that i would like the user to be able to update.

class EZ_Schein_Oange(models.Model):

Teilnehmer_Nummer = models.IntegerField(blank=False, primary_key=True)
BESR_Nr = models.IntegerField(blank=True)

def __str__(self):
    return str(self.Teilnehmer_Nummer)
class Einzahlung_Fuer(models.Model):

Bank = models.CharField(max_length=120, blank=False)
Adresse = models.CharField(max_length=120, blank=False)

def __str__(self):
    return self.Bank
class Zugunsten_Von(models.Model):

Name = models.CharField(max_length=120, blank=False)
Zusatz = models.CharField(max_length=120, blank=False)
Adresse = models.CharField(max_length=120, blank = True)
PLZ = models.IntegerField(blank=True)
Ort = models.CharField(max_length=120, blank=True)

def __str__(self):
    return self.Name

forms.py

class EZ_Schein_OangeForm(forms.ModelForm):

Teilnehmer_Nummer = forms.CharField(label='Teilnehmer-Nummer', widget=forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'VESR Teilnehmernummer'}))
BESR_Nr = forms.CharField(label='BESR-Nr', required=False, widget=forms.TextInput(attrs={'class': 'form-control', 'placeholder': '6-10 Stelliges Kundennummer'}))

class Meta:
    model = EZ_Schein_Oange
    fields = [ 'Teilnehmer_Nummer','BESR_Nr' ]
class Einzahlung_FuerForm(forms.ModelForm):

Bank = forms.CharField(label='Bank', widget=forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Bank'}))
Adresse = forms.CharField(label='Adresse', widget=forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Adresse'}))

class Meta:
    model = Einzahlung_Fuer
    fields = [ 'Bank', 'Adresse']
class Zugunsten_VonForm(forms.ModelForm):

Name = forms.CharField(label='Name', widget=forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Name'}))
Zusatz = forms.CharField(label='Zusatz', required=False,  widget=forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Zusatz'}))
Adresse = forms.CharField(label='Adresse', widget=forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Adresse'}))
PLZ = forms.CharField(label='PLZ', widget=forms.TextInput(attrs={'class': 'form-id', 'placeholder': 'PLZ'}))
Ort = forms.CharField(label='Ort', widget=forms.TextInput(attrs={'class': 'form-id', 'placeholder': 'Ort'}))

class Meta:
    model = Zugunsten_Von
    fields = [ 'Name', 'Zusatz', 'Adresse', 'PLZ', 'Ort' ]

views.py

def bank_edit(request):
            instance = get_object_or_404(EZ_Schein_Oange)
            form = EZ_Schein_OangeForm(request.POST or None, instance=instance)
            form2= Einzahlung_FuerForm(request.POST or None, instance=instance)            
            form3 = Zugunsten_VonForm(request.POST or None, instance=instance)

            title = 'EZ-Schein orange (ESR)'
            title2 = 'Einzahlung fuer'
            title3 = 'Zugunsten von'

            bankverbindung_app = EZ_Schein_Oange.objects.all()
            bankverbindung_app2 = Einzahlung_Fuer.objects.all()
            bankverbindung_app3 = Zugunsten_Von.objects.all()

            context = {
                        "title": title,
                        "title2": title2,
                        "title3": title3,
                        "form2": form2,
                        "form3": form3,
                        "bankverbindung_app": bankverbindung_app,
                        "bankverbindung_app2": bankverbindung_app2,
                        "bankverbindung_app3": bankverbindung_app3,
                        "instance": instance,
                        "form": form,


            }
            #if request.method == 'POST':
            if form.is_valid():

                        form = EZ_Schein_OangeForm(instance=instance, data=request.POST)

                        instance = form.save(commit=False)
                        instance.save()

                        return render(request, 'bankverbindung.html', context)

                        print("error: form not valid")

            return render(request, 'bank_edit.html', context)