Magento 2 Database – Get All Column Names of Table

1) I Assume you have created Model and Collection file associated with that tables.

2) In a Block PHP file constructor add one argument (Dependency Injection) like below and store it in a class member variable.

 public function __construct(
    Context $context,
    \Namespace\Modulename\Model\ModelNameFactory $modelNameFactory,

    array $data = array()
) {
    $this->_modelFactory = $modelFactory;
    parent::__construct($context, $data);
}

3) Prepare a public method in your block to access collection like below.

public function getCollection(){

    return $this->_modelFactory->create()->getCollection();

}

4) Loop through each of the collection result.

Hope, this will help you.

Create a controller in your Vendor/Modlue/Controller/Index

    <?php

namespace Vendor\Module\Controller\Index;

use Magento\Framework\Controller\ResultFactory;
use Magento\Framework\App\Action\Context;
use Vendor\Module\Model\YourModel;
class Blog extends \Magento\Framework\App\Action\Action
{
    protected $model;
    protected $date;
    protected $customermodel;

    public function __construct(
        Context $context,
        YourModel $model,
        \Magento\Framework\Stdlib\DateTime\DateTime $date
    )
    {
        $this->model = $model;
        $this->date = $date;
        parent::__construct($context);
    }

    public function execute()
    {
        $query['question'] = $this->getRequest()->getPostValue("question");
        $query['email'] = $this->getRequest()->getPostValue("email");
        $query['product_name']=$this->getRequest()->getPostValue("product_name");
        $query['cutomer_name']=$this->getRequest()->getPostValue("customer_name");

        if ($query){

        $this->model->setData($query);
        $this->model->Save();
        $redirect = $this->resultFactory->create(ResultFactory::TYPE_REDIRECT);
        $redirect->setUrl($this->_redirect->getRefererUrl());
        $this->messageManager->addSuccess(__('You submitted your Question successfully.'));
        return $redirect;
        }
        else{
            $redirect = $this->resultFactory->create(ResultFactory::TYPE_REDIRECT);
            $redirect->setUrl($this->_redirect->getRefererUrl());
            $this->messageManager->addError (__('Failed To Submit  Please Provide Valid Data.'));
            return $redirect;
        }
    }
}