The task was to create something like this without any teacher's help:
How I built my website:
It's pretty clear that the website above consists of 3 sections. So firstly I created 3 sections by using semantic elements such as header, main, footer, and a section in each of them.
I gave them classes and placed them in a flex container for centering the whole page content.
I created a hero section, activities, and a card using flexbox, too.
I made the activities section responsive by using flex-wrap:wrap.
I made a background image responsive with background-size and background-position properties. The key was to hide an overflow on the x-axis so it can adjust to smaller screen sizes.
I made the code DRYer by creating a utility class for padding.