Answers for "how to set width to screen size css"

css image size adjust

squareImage {
  border: 1px solid #ddd;	/* thickness and color of border */
  border-radius: 4px;		/* edge rounding of border */
  width: 150px;				/* width of image (px or % or auto) */
  height: auto;				/* height of image (px or % or auto) */
}

width in % of a screen css

1vw = 1% of viewport width
1vh = 1% of viewport height