TEST

$productCollection = $objectManager->create('Magento\Catalog\Model\ResourceModel\Product\Collection');

$productLink = $objectManager->create('Magento\Catalog\Api\Data\ProductLinkInterface');
$collection = $productCollection
->addAttributeToSelect('*')
->addFieldToFilter('visibility', 4)
->addFieldToFilter('status',1)
->addAttributeToFilter('kolekcja', ['notnull' => true], 'left')->load();
$array = array();
$i = 0;
$linkData = array();
foreach ($collection as $product){


    if(!count($product->getUpSellProductIds()) > 0):

    $productCollection2 = $objectManager->create('Magento\Catalog\Model\ResourceModel\Product\Collection');
    $collection2 = $productCollection2
    ->addAttributeToSelect('*')
    ->addFieldToFilter('visibility', 4)
    ->addFieldToFilter('status',1)
    ->addAttributeToFilter('kolekcja', $product->getKolekcja())
    ->addAttributeToFilter('producent',$product->getProducent())->load();

        if($collection2):
            $r = 1;

            unset( $linkData );
            foreach($collection2 as $product2):

               echo $product2->getId().'</br>';
               $productLink = $objectManager->create('Magento\Catalog\Api\Data\ProductLinkInterface')
            ->setSku($product->getSku())
            ->setLinkedProductSku($product2->getSku())
            ->setPosition($r)
            ->setLinkType('upsell');
        $r++;
        $linkData = $product->getProductLinks();
        $linkData[] = $productLink;
        $product->setProductLinks($linkData)->save();
            endforeach;

        endif;


    echo $product->getName();

endif;