Hi @eunjinyun

Please replace the following code in the style.css file of the child theme.

Replace

@import url("../novapress-pro/style.css");

With

@import url("../novapress-pro/css/theme.min.css");
@import url("../novapress-pro/css/multi-columns-row.css");
@import url("../novapress-pro/style.css");

To do this go to Appearance > Editor and edit the style.css file.