I'm trying to make a page design like this one: click
I made it, actually. Problem is that when I change the resolution of my webpage, the elements overlap, the background div and the PNG acts different and everything looks awful. (I've tried with position: absolute (PNG) and position: relative (background))
You can use the background-size and background-position CSS properties. You should try this way:
body {
background-image: url("your-bg-image.jpg");
background-size: cover;
background-position: center;
}
.responsive-image {
background-image: url("your-image.png");
background-size: contain;
background-position: center;
width: 100%;
height: 100%;
}