I tried to search many posts about this problem and any one those couldn't solve my problem sadly and I couldn't understand on some points.This is the post.
Django cannot find static files. Need a second pair of eyes, I'm going crazy
I guess this is the most similar case with me and someone gave very nice answer for it, but it couldn't solve my problem :/
This is my file set
- beerlog  
 - beerlog
     - settings.py
     - ...
 - posting
     - urls.py
     - templates
         - posting
             - base.html
             - index.html
             - post.html
             - posting.html
     - static
         - posting
             - style.css
         - ...
 - static
     - registration
         - ...
settings.py
STATIC_URL = '/static/'
STATIC_ROOT = os.path.join(BASE_DIR, 'static')
MEDIA_URL = '/media/'
MEDIA_ROOT = os.path.join(BASE_DIR, 'media')
/posting/templates/posting/base.html
<!DOCTYPE html>
{% load static %}
<html class="no-js">
    <head>
        <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <title>Beerlog</title>
        <meta name="description" content="">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <link rel="stylesheet" href="/posting/sytle.css">
        {% block extra_head %}{% endblock %}
    </head>
    <body>
        <h2 class='headline'>Welcome to beerlog!</h2>
        <ul class="sidenav">
            {% if user.is_authenticated %}
            <li>Welcome back {{ user.get_username }}!</li>
            <li><a href="{% url 'logout' %}?next={{request.path}}">Logout</a></li>
            {% else %}
            <li><a href="{% url 'login' %}?next={{request.path}}">Login</a></li>
            {% endif %}
        </ul>
        {% block content %}
        {% endblock %}
/posting/urls.py
from django.urls import path
from django.conf import settings
from django.conf.urls.static import static
from . import views
app_name = 'posting'
urlpatterns = [
    path('', views.index, name='index'),
    path('<int:post_id>', views.post, name='post'),
    path('posting', views.posting, name='postingform'),
    path('base', views.base, name='base')
]
/beerlog/urls.py
from django.contrib import admin
from django.urls import path, include
from django.contrib.staticfiles.urls import static, staticfiles_urlpatterns
from . import settings
urlpatterns = [
    path('posting/', include('posting.urls')),
    path('admin/', admin.site.urls),
]
urlpatterns += staticfiles_urlpatterns()
urlpatterns += static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)
urlpatterns += [
    path('accounts/', include('django.contrib.auth.urls')),
]
I set static file same as django official documents like templates, templates work well but why css doeesn't work? Please help me guys :( Desperate