Updating the theme via WordPress is very similar to the install process via WordPress. Follow the steps below to update your theme via WordPress:
Step 1: Log into marketplace where you buy this theme and download updated version.
Step 2: You need to deactivate the current deKor theme located in Appearance --> Themes section by activating a different theme. Once you activate a different theme, you can delete deKor theme. Don't worry, your content will not be lost
Step 3: Unzip the new theme package you've downloaded and open theme folder of your theme version. You can see .zip file inside.
Step 4: Upload this zip file to Appearance --> Themes section by clicking on the Install Themes tab at the top.
Step 5: Once it finishes uploading, choose to activate the theme.
Step 6: Lastly, update the included plugins. You will see a notification message letting you know a new version of the plugins are available and need to be updated.
Please try to update your site. If the problem still appears, please make your site go live so that we can check it for you.
I've tested your site but not see the problem.
Please see my attachment.
Maybe you can try using smaller images to be featured images of portfolios. By this way, your portfolio page will be loaded quickly and completely.