Background for Responsive Design

Hi guys,

So I am doing the FreeCodeCamp portfolio. I designed it using Sketch and started coding it.
Things are fine for now for the desktop. However, I am struggling with the mobile version.

Is there any tips to adapt my background image to the background for the mobile version?

Below you will find the two screenshot of what I would like to realize.
Could I use SVG for background ? Or should I use another background using media queries ?

Thank you
if you are using bootstrap ,this may help your image resize automatically