section full width

ok – now i see the pages . There are elements in it.
to have a color-section with background-image responsive you had to determine the height in that aspect-ratio of the bg image.
for your page (free-session) i would insert the 1500px x 430px image format – and set the background-image to cover.

Then for your page: free-session

#top.page-id-9607 #av_section_1 {
  height: 28.66vw; /***  100x(430px:1500px)  ***/
  min-height: 350px;
  background-size: cover !important; /*** but you can do that on alb settings ***/
}

The min-height rule is to have enough height on small screens to fully surround the content

Same on your home page – let the image be full and set background-size to cover

#top.page-id-143 #av_section_3 {
  height: 26.04vw; /***  100x(500px:1920px)  ***/
  min-height: 500px;
  background-size: cover !important; /*** but you can do that on alb settings ***/
}