Hi there,
Welcome to SeaTheme forum.

Do you mean that the data in the “import demo” has been lost? Are you using Child theme?
Please check if it work to stop the child theme.

If I don’t understand your question, please provide some details (it’s better to paste a screenshot), thanks!

Regards!
SeaTheme – FAQs – Twitter – Facebook

Hi, thanks for your screenshots

For license reason, the placeholder images(colorful images) replace the demo pictures. You could replace them with your own images.
Please go to Portfolio > All Portfolio:

Please go to Portfolio >

Edit each single portfolios, replace the Featured image as your own image(the featured image is for the thumbnail of the portfolio list):

Click BM Content Builder to enter the builder panel, click the pencil, edit the module to replace images in the single portfolio(project) page.

https://doc.seatheme.net/theme/art/installation/installing-art-via-wordpress/#replace-the-placeholders

Regards!
SeaTheme – FAQs – Twitter – Facebook