<?php
namespace Catalog\Product\Controller\Index;
use Magento\Framework\App\Action\Action;
use Magento\Framework\App\Action\Context;
use Magento\Framework\Data\Form\FormKey;
use Magento\Checkout\Model\Cart;
use Magento\Catalog\Model\Product;
class Index extends Action
{
    protected $resultPageFactory;
    protected $formKey;   
    protected $cart;
    protected $product;
    public function __construct(
        \Magento\Framework\View\Result\PageFactory $resultPageFactory,
        Context $context,
        FormKey $formKey,
        Cart $cart,
        Product $product) {
            $this->formKey = $formKey;
            $this->cart = $cart;
            $this->product = $product;     
            $this->resultPageFactory = $resultPageFactory;
            parent::__construct($context);
    }
    public function execute()
     { 
        $resultRedirect = $this->resultRedirectFactory->create();
     
        $simple_collection = array('6171','6172','6173');
        $count = 1;
        foreach($simple_collection as $simple_product){
            
            ${'prodAddId'.$count} = $_POST['prodCol'.$count.''];
            if( $_POST['qtyCol'.$count.''] > 0 ){
                ${'params'.$count} = array(
                            'form_key' => $this->formKey->getFormKey(),
                            'product' => ${'prodAddId'.$count} , 
                            'qty'   => $_POST['qtyCol'.$count.'']
                        );              
                ${'productCart'.$count} = $this->product->load( ${'prodAddId'.$count} ); 
                $this->cart->addProduct( ${'productCart'.$count} , ${'params'.$count} );
                
            } 
            
        $count++;
        }
        $this->cart->save();
        return $resultRedirect->setPath('checkout');
     }
}
?>

How can I put all the various simple products in the cart and update minicart?

<?php
namespace Catalog\Product\Controller\Index;
use Magento\Framework\App\Action\Action;
use Magento\Framework\App\Action\Context;
use Magento\Framework\Data\Form\FormKey;
use Magento\Checkout\Model\Cart;
use Magento\Catalog\Model\Product;
class Index extends Action
{
    protected $resultPageFactory;
    protected $formKey;   
    protected $cart;
    protected $product;
    public function __construct(
        \Magento\Framework\View\Result\PageFactory $resultPageFactory,
        Context $context,
        FormKey $formKey,
        Cart $cart,
        Product $product) {
            $this->formKey = $formKey;
            $this->cart = $cart;
            $this->product = $product;     
            $this->resultPageFactory = $resultPageFactory;
            parent::__construct($context);
    }
    public function execute()
     { 
        //INSERIMENTO NEL CARRELLO PER PROD CONFIGURABILE   
        if($_POST['productType'] == 'configurable'){    
            $resultRedirect = $this->resultRedirectFactory->create();
            $prodIdColl = $this->product->load($_POST['productID']);
            $simple_collection = array('valore1','valore2','valore3');
            $count = 1;
            
            foreach($simple_collection as $simple_product){
                
                ${'prodAddId'.$count} = $_POST['prodCol'.$count.''];
                if( $_POST['qtyCol'.$count.''] > 0 ){
                    ${'params'.$count} = array(
                                'form_key' => $this->formKey->getFormKey(),
                                'product' => ${'prodAddId'.$count} , 
                                'qty'   => $_POST['qtyCol'.$count.'']
                            );              
                    ${'productCart'.$count} = $this->product->load( ${'prodAddId'.$count} ); 
                    $this->_cart->addProduct( ${'productCart'.$count} , ${'params'.$count} );
                    
                } 
                
            $count++;
            }
            $this->_cart->save();
            return $resultRedirect->setPath('checkout');
        }
        
        //INSERIMENTO NEL CARRELLO PER PROD SEMPLICE
        if($_POST['productType'] == 'simple'){
            $resultRedirect = $this->resultRedirectFactory->create();
            $productId = $_POST['productID'];
            $params = array(
                        'form_key' => $this->formKey->getFormKey(),
                        'product' => $productId, 
                        'qty'   => $_POST['qtySimple']
                    );              
            $product = $this->product->load($productId);       
            $this->_cart->addProduct($product, $params);
            $this->_cart->save();
            return $resultRedirect->setPath('checkout');
        }
     }
}
?>

How can I put all the various simple products in the cart?

Issue with my script: The problem is that this script only adds one product to the cart and not all the other simple products. The quantities instead the sums. For example, if I want to add 3 simple products to the cart, I only add the first one and add the quantities of all 3