Yii2 backend UrlManager not working properly - php

Question

I've got a problem with my backend url manager which is obviously doing different thing then my frontend.
frontend url: www.example.com/frontend/web/site/index
backend url: www.example.com/backend/web/index.php/site/login
Both urls are working when request like above. But when i call the backend url like frontend without the index.php, i just receive 404. Also my site/index is not working, because when i enter it trough backend/web/index.php/site/index, i get redirected to backend/web/index.php/site/login immediatly. I thinkg those two have the same problem. But it is strange, because both main.php are almost equally:
SOLUTION: Missing /backend/web/.htaccess file
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . index.php
frontend/config/main.php
<?php
$params = array_merge(
require __DIR__ . '/../../common/config/params.php',
require __DIR__ . '/../../common/config/params-local.php',
require __DIR__ . '/params.php',
require __DIR__ . '/params-local.php'
);
return [
'id' => 'app-frontend',
'basePath' => dirname(__DIR__),
'bootstrap' => ['log'],
'controllerNamespace' => 'frontend\controllers',
'components' => [
'request' => [
'csrfParam' => '_csrf-frontend',
],
'user' => [
'identityClass' => 'common\models\User',
'enableAutoLogin' => true,
'identityCookie' => ['name' => '_identity-frontend', 'httpOnly' => true],
],
'session' => [
'name' => 'advanced-frontend',
],
'log' => [
'traceLevel' => YII_DEBUG ? 3 : 0,
'targets' => [
[
'class' => 'yii\log\FileTarget',
'levels' => ['error', 'warning'],
],
],
],
'errorHandler' => [
'errorAction' => 'site/error',
],
'urlManager' => [
'enablePrettyUrl' => true,
'showScriptName' => false,
],
],
'params' => $params,
];
backend/config/main.php
<?php
$params = array_merge(
require __DIR__ . '/../../common/config/params.php',
require __DIR__ . '/../../common/config/params-local.php',
require __DIR__ . '/params.php',
require __DIR__ . '/params-local.php'
);
return [
'id' => 'app-backend',
'basePath' => dirname(__DIR__),
'controllerNamespace' => 'backend\controllers',
'bootstrap' => ['log'],
'modules' => [],
'components' => [
'request' => [
'csrfParam' => '_csrf-backend',
],
'user' => [
'identityClass' => 'common\models\User',
'enableAutoLogin' => true,
'identityCookie' => ['name' => '_identity-backend', 'httpOnly' => true],
],
'session' => [
'name' => 'advanced-backend',
],
'log' => [
'traceLevel' => YII_DEBUG ? 3 : 0,
'targets' => [
[
'class' => 'yii\log\FileTarget',
'levels' => ['error', 'warning'],
],
],
],
'errorHandler' => [
'errorAction' => 'site/error',
],
'urlManager' => [
'enablePrettyUrl' => true,
'showScriptName' => false,
],
],
'params' => $params,
];
I would be glad if someone could help me with this. Please just ask for furth or missing informations.