How to override form field in Django function based view?

I like to use a form in a function based view but I like to override the kategoria select field to show only the objects that related to the user.

models.py

class Blog_poszt(models.Model):    def __str__(self):        return str(self.user)    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="blog_szerzo")    datetime = models.DateTimeField(auto_now_add=True, auto_now=False)    cim = models.CharField(max_length=300)    cim_slug = models.CharField(max_length=300, null=True, blank=True)    szoveg = models.CharField(max_length=10000, null=True, blank=True)    kategoria = models.ForeignKey('Blog_kategoriak', on_delete=models.CASCADE, null=True, blank=True)    kep = models.FileField(upload_to="blog/", null=True, blank=True)class Blog_kategoriak(models.Model):    def __str__(self):        return str(self.user)    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="kategoria_szerzo")    datetime = models.DateTimeField(auto_now_add=True, auto_now=False)    kategoria = models.CharField(max_length=200)

forms.py

class UjBlogposztForm(forms.ModelForm):    class Meta:        model = Blog_poszt        fields = '__all__'        exclude = ('user',) 

views.py

def blog_poszt(request):    form = UjBlogposztForm(request.POST, request.FILES)    if request.method == 'POST':        if form.is_valid:            form.instance.user = request.user            form.save()    context = {'form': form,    }

html

<form method="post" enctype="multipart/form-data">    {% csrf_token %}         {{ form.as_p }}<button type="submit" class="btn btn-dark">Mentés</button></form>