controller.php

<?php
    /**
     * @return \Cake\Http\Response|null
     */
    public function add()
    {
        $vendorId = $this->request->getData('vendor_id');

        if (empty($vendorId)) {
            $vendorId = $this->request->getQuery('vendor_id');
        }

        $vendor = $this->VendorProductPriceFiles->CompaniesVendors->Vendors->get($vendorId);
        $companiesVendor = $this->CompaniesVendors->findOrCreate([
            'CompaniesVendors.company_id' => $this->Auth->user('company_id'),
            'CompaniesVendors.vendor_id' => $vendor->id,
        ]);

        if ($this->request->is(['POST'])) {
            $companiesVendor = $this->CompaniesVendors->patchEntity($companiesVendor,[
                'delivery_price' => $this->request->getData('delivery_price'),
                'free_delivery_price' => $this->request->getData('free_delivery_price'),
            ]);
            $vendorProductPriceFile = $this->VendorProductPriceFiles->newEntity([
                'vendor_id' => $this->request->getData('vendor_id'),
                'file' => $this->request->getData('file'),
                'companies_vendor' => $companiesVendor,
            ]);

            if ($this->VendorProductPriceFiles->save($vendorProductPriceFile)) {
            //
            }
        //
        }

        $this->set(compact('vendor'));
    }