HTML and Basic CSS with Flexbox is used.

Hello there!

This looks good! As for your question about background images being in the HTML or CSS, generally all styling should be in the CSS unless for some reason it can't be (e.g images being dynamically added via JS) so the way you have done background images here is correct.

Another couple of bits and pieces:

1. It's great that you've added alt text to your images, but you don't need to add the word 'pic' as it's already assumed your alt text is referring to an image.
2. When using 0 values in your CSS you don't need to add px, em or rem at the end e.g margin: 0 is just fine!

Hello, Do you know about screenshots ? I don't know where to collect them.I clicked at an option but don't know where is that..