In CategoriesTable.php:

public function initialize(array $config)
   {
      $this->belongsTo('ParentCategories', ['className' => 'Categories', 'foreignKey' => 'parent_id']);
      $this->hasMany('ChildCategories', ['className' => 'Categories', 'foreignKey' => 'parent_id']);
      $this->hasMany('Resources', ['sort' => ['Resources.uri' => 'ASC']]);
      $this->hasMany('ResourcesCounts', ['foreignKey' => 'category_id']);
   }

In ResourcesController.php

$catcount =  $this->Resources->Categories->find('all')
               ->contain(['ResourcesCounts'])
               ->group(['ResourcesCounts.date'])
               ->order(['ResourcesCounts.date' => 'ASC'])
               ->where([
                    'ResourcesCounts.date BETWEEN DATE_SUB("'.$start_of_month->format('Y-m-d 00:00:00').'", INTERVAL '.$day_month_starts.' DAY) AND DATE_ADD("'.$start_of_month->format('Y-m-t 23:59:59').'", INTERVAL '.(7 - $day_month_ends).' DAY)',
                    'Categories.lft >='  => $showcat->category['lft'],
                    'Categories.rght <=' => $showcat->category['rght'],
                ]);