@Sudeshna1992,
When dealing with XF, its good practice create and overlay your own xf base page (/apps/my-site/components/structure/xfpage). This gives flexibility to overlay existing scripts and files without doing tricky things like overwriting CSS or JS for the resources & components within /libs.
At a glimpse, /libs/cq/experience-fragments/components/xfpage/content.css looks like styles Adobe added to enhance the authoring experience or to ensure that the component has a min-height... looks to me that content.css is not significant, and will not cause any broken behavior, so your own xf base page, and overlay .content.css, and leave this file empty.
I hope this helps.