Make a HTML One-Page Responsive

Hi,
I have an HTML template that i want to be responsive.

Here is the template :
https://biorecos.cerballiance.fr/wp-content/responsive/index.html

Here is how i want it to be responsive :
https://xd.adobe.com/view/f386c322-8e72-4a8d-8537-d185f2f74c31-a6d5/