How to use ajax with django forms?

My models.py

# -*- encoding: utf-8 -*-
from django.db import models
from general.models import BaseUnique, BaseTitle, Empresa, Arl
from recurso_humano.models import Persona, Sucursal

# ===================== HEALTH BASIC =========================
TIPO_DOCUMENTO = (
    (1, 'Cédula'),
    (2, 'Nit'),
)

class Especialidad(BaseUnique):
    pass

class ProveedorSalud(models.Model):
    tipo_documento = models.IntegerField(choices=TIPO_DOCUMENTO, verbose_name="tipo de Identificación")
    numero_documento = models.BigIntegerField(unique=True, verbose_name='número de Identificación')
    nombre_completo = models.CharField(max_length=255, verbose_name='Nombre Completo')
    telefonos = models.CharField(max_length=255, verbose_name='Teléfono(s)')
    especialidades = models.ManyToManyField(Especialidad, blank=True, through='ProveedorEspecialidad', related_name="esp")

    def __str__(self):
        return ("%s"%(self.nombre_completo)).strip() or "-"

class ProveedorEspecialidad(models.Model):
    proveedor = models.ForeignKey(ProveedorSalud)
    especialidad = models.ForeignKey(Especialidad)

class DatosExamenMedico(models.Model):
    codigo = models.CharField(max_length=255)
    nombre = models.CharField(max_length=255, verbose_name="Nombre Exámen")
    proveedor = models.ForeignKey(ProveedorSalud)
    especialidad = models.ForeignKey(Especialidad)
    precio_de_proveedor = models.IntegerField(verbose_name="Precio de Proveedor")
    precio_a_cliente = models.IntegerField(verbose_name="Precio a Cliente")

    class Meta:
        unique_together = (("codigo", "nombre"),)

    def __str__(self):
        return ("%s (%s)"%(self.codigo, self.nombre)).strip() or "-"

My initial forms.py

# -*- encoding: utf-8 -*-
import random, string, os

from django import forms
from django.forms import ModelForm
from django_select2.forms import Select2MultipleWidget, Select2Widget
from django.contrib.auth.models import User
from django_select2.forms import ModelSelect2Widget, Select2Widget

from gestion_salud.models import *
from general.models import Empresa, Arl, ActividadEconomica, Empresa_ActividadEconomica

class DatosExamenMedicoForm(forms.ModelForm):
    class Meta:
        model = DatosExamenMedico
        exclude = ()
        widgets = {
        }

class EspecialidadForm(forms.ModelForm):
    class Meta:
        model = Especialidad
        exclude = ()

class ProveedorSaludForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(ProveedorSaludForm, self).__init__(*args, **kwargs)
        self.fields['especialidades'].queryset = Especialidad.objects.all()

    class Meta:
        model = ProveedorSalud
        exclude = ()
        widgets = {
            'especialidades': Select2MultipleWidget()
        }

Part of my views.py

# -*- encoding: utf-8 -*-
from django.http import Http404
from django.shortcuts import redirect, render
from django.contrib.auth.decorators import login_required

from gestion_salud.forms import *
from recurso_humano.forms import PersonaForm, PersonaForm_Basico, CedulaForm
from recurso_humano.models import Persona
from recurso_humano.views.gestion_humana import calcular_tipo

@login_required
def examen_medico_crear(request):    
    if request.method == 'POST':
        form = DatosExamenMedicoForm(request.POST, request.FILES)
        if form.is_valid():
            objeto = form.save(commit=False)
            objeto.save()
            request.session['em_creada'] = True
            return redirect('matriz_em')
    else :
        form = DatosExamenMedico_crear_Form()

    return render(request, 'em_crear__salud.html', {
        'form': form,
    })

It turns out that if I send the default form for DatosExamenMedico I can select any ProveedorSalud and any Especialidad , but the idea is not that, but first select the provider and automatically in the field Especialidad filtren only the specialties of that ProveedorSalud .

I have been told to use ajax, but I do not know how to find the info I need, neither in Spanish nor in English, an example would be very helpful, even if it is from countries-cities.