Django Image field doesn't update image

I recently got a problem that my django image field in my django app doesn't update the image after pressing "Post". In admin panel everything works fine. Maybe I missed something... Let me know.

models.py

from django.db import models
from django.utils import timezone
from django.contrib.auth.models import User
from django.urls import reverse

class Post(models.Model):
    title = models.CharField(max_length=200)
    content = models.TextField()
    date_posted = models.DateTimeField(default=timezone.now)
    author = models.ForeignKey(User, on_delete=models.CASCADE)
    categories = models.ManyToManyField('Category', related_name='posts')
    image = models.ImageField(upload_to='images', default="images/None/no-img.jpg")



    def __str__(self):
        return self.title

    def get_absolute_url(self):
        return reverse('post-detail', kwargs={'pk': self.pk})


class Category(models.Model):
    name = models.CharField(max_length=20

)

views.py

from django.shortcuts import render, get_object_or_404
from django.contrib.auth.mixins import LoginRequiredMixin, UserPassesTestMixin
from .models import Post
from django.contrib.auth.models import User
from django.views.generic import ListView, DetailView, CreateView, UpdateView, DeleteView


def home(request):
    content = {
        'posts': Post.objects.all()
    }

    return render(request, 'blog/home.html', content)

def blog_category(request, category):
    posts = Post.objects.filter(categories__name__contains=category).order_by('-date_posted')
    content = {
        'category': category,
        'posts': posts
    }
    return render(request, 'blog/blog_category.html', content) #<--(didn't add content block) bug found 05.11.19

def upload_pic(request):
    if request.method == 'POST':
        form = ImageUploadForm(request.POST, request.FILES)
        if form.is_valid():
            m = ExampleModel.objects.get(pk=course_id)
            m.model_pic = form.cleaned_data['image']
            m.save()
            return HttpResponse('image upload success')
    return HttpResponseForbidden('allowed only via POST')

...

class PostCreateView(LoginRequiredMixin, CreateView):
    model = Post
    fields = ['title', 'content', 'categories', 'image']

    def form_valid(self, form):
        form.instance.author = self.request.user
        return super().form_valid(form)


class PostUpdateView(LoginRequiredMixin, UserPassesTestMixin, UpdateView):
    model = Post
    fields = ['title', 'content', 'categories', 'image']

    def form_valid(self, form):
        form.instance.author = self.request.user
        return super().form_valid(form)

I just have recently added Category and Image section in my web-application, the Category section works fine, but the image field just post default even if I'm selecting the current image. In the admin field it works well, so I decided to ask community about this annoying problem.

Make sure the form in your template has enctype set correctly:

Note that request.FILES will only contain data if the request method was POST and the that posted the request has the attribute enctype="multipart/form-data". Otherwise, request.FILES will be empty.