Magento2 has a built-in script for any kind of file download, we can use the below code for file downloads:

<?php
/**
 * Magemonkeys.
 *
 * @category  Magemonkeys
 *
 * @author    Magemonkeys
 * @copyright Copyright (c) 2020 Magemonkeys (https://magemonkeys.com/)
 */

namespace MagemonkeysDownloadControllerDownload;

use MagentoFrameworkAppActionContext;

/**
 * file download controller.
 */
class Index extends MagentoFrameworkAppActionAction
{
    /**
     * @var MagentoFrameworkAppResponseHttpFileFactory
     */
    protected $_downloader;

    /**
     * @var MagentoFrameworkFilesystemDirectoryList
     */
    protected $directory;

    /**
     * @param Context     $context
     * @param PageFactory $resultPageFactory
     */
    public function __construct(
        Context $context,
        MagentoFrameworkAppResponseHttpFileFactory $fileFactory,
        MagentoFrameworkFilesystemDirectoryList $directory
    ) {
        $this->_downloader =  $fileFactory;
        $this->directory = $directory;
        parent::__construct($context);
    }

    public function execute()
    {
        $fileName = $this->getRequest()->getParam('fileName');
        $file = $this->directory->getPath("media")."/FilePath/".$fileName;
        // do your validations

        /**
         * do file download
         */
        return $this->_downloader->create(
            $fileName,
            @file_get_contents($file)
        );
    }
}