Here are what I've done in the last week:

• Finished coding that (from the week before) landing page from PSD.
• Studied CSS transitions and animations, CSS transform 2d and 3d
• Studied how to embed video on a page including background video
• Started with CSS Grid

Mistakes:

• Images in CSS code rather than in HTML. backround-image for div instead of img in HTML - not the best option.
• Split menu on two separate blocks (because of the logo in the middle), no need for that, though.
• Mirroring blocks in HTML instead of CSS (same structure, but reversed)
• flex: wrap instead of flex-direction: column with media queries for screen width.

Notes:

• If background-size: cover — not working, it needs to come AFTER background in your code.
• Good code quality HTML/CSS layout won't break if you add more text, less text or another sized images.