yii2 routing and htaccess configuration

Question

I have the following directories in my project:

• Project:
  • frontend: (which is the angularjs app)
  • backend: (which is the yii2 advanced app)
    • backend:
      • controllers
      • models
      • views
      • web: the root of backend (index.php)
    • frontend:
      • controllers
      • models
      • views
      • web: the root of frontend (index.php)

I want to point to the backend (yii2 app) by this URL : http://localhost/Project/backend, while the frontend (angular) should be the root, which is http://localhost/Project. and so on, I want to call the controller api by this URL: http://localhost/Project/backend/api.

what I've tried so far:

.htaccess (Project):

Options +FollowSymlinks
RewriteEngine On

RewriteCond %{REQUEST_URI} ^/Project
RewriteRule ^.*$ frontend/backend/web/index.php [L]

RewriteCond %{REQUEST_URI} ^/obeauty/(admin)
RewriteRule ^.*$ backend/backend/web/index.php [L]

.htaccess (Project/backend):

Options +FollowSymlinks
RewriteEngine On

RewriteCond %{REQUEST_URI} ^/Project/(backend)
RewriteRule ^backend/assets/(.*)$ backend/web/assets/$1 [L]
RewriteRule ^backend/css/(.*)$ backend/web/css/$1 [L]

.htaccess (Project/backend/backend):

RewriteEngine On 
RewriteCond %{REQUEST_FILENAME} !-f 
RewriteCond %{REQUEST_FILENAME} !-d 
RewriteRule ^(.*)$ /index.php?/$1 [L]

Request.php (Project/backend/common/components):

<?php

namespace common\components;

class Request extends \yii\web\Request {
    public $web;
    public $adminUrl;

    public function getBaseUrl(){
        return str_replace($this->web, "", parent::getBaseUrl()) . $this->adminUrl;
    }

    public function resolvePathInfo(){
        if($this->getUrl() === $this->adminUrl){
            return "";
        }else{
            $pathInfo = parent::resolvePathInfo();
            return $pathInfo == 'index.php' || $pathInfo == 'index.php/' ? 'site/index' : $pathInfo;
        }
    }
}

main.php (Project/backend/backend/config):

<?php

return [
    'id' => 'app-backend',
    'basePath' => dirname(__DIR__),
    'controllerNamespace' => 'backend\controllers',
    'bootstrap' => ['log'],
    'modules' => [],
    'components' => [
        'request' => [
            'csrfParam' => '_csrf-backend',
            'class' => 'common\components\Request',
            'web'=> '/backend/web',
            'adminUrl' => '/backend'
        ],
        'urlManager' => [
            'enablePrettyUrl' => true,
            'showScriptName' => false,
            'rules' => [
                'api-create' => 'api/api-create',
                'api' => 'api/api',
                'mobileapi/<action:\w+>' => 'mobileapi/<action>' 
            ],
        ],
    ],
];