Thank you for sharing the site details.

I can see you are using older version 2.0.3 of  theme on your site so could you please try updating it to the latest version?

I can see the page http://tkparnas.info/portfolio/kukhni-vardek/ is working but not http://tkparnas.info/portfolio/

Can you please try temporary enabling WP_DEBUG mode? To do this, just go to wp-config.php include this:

define('WP_DEBUG',true);

You might already have a line for WP_DEBUG, so just make sure it’s set to true.

Let me know what errors if any you are getting on the portfolio page.