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.