Responsive page using pure CSS

What are you most proud of, and what would you do differently next time?

Practising some grid with autofill.

What challenges did you encounter, and how did you overcome them?

Some problems can be found on the Instagram gradient, but with ::before everything got solved.

What specific areas of your project would you like help with?

I don't know if the top background is static or not, but I can't find any way to make it relative to its position and having the width of the parent element (body). Some recommendations??

Any other suggestions are welcomed.