This image shows an example of bad user experience: no clear borders/shadows of the drop-down menu; a big gap between the text link and the menu.
So when users hover on the gap area without notice it, the menu automatically collapsed.

Another example is the alignment of text.
Alignment is very important. It can be very hard to read if the text is right-aligned, especially when there are some long paragraphs in the text.

Consistency is one of the golden principles in design.
It means when I'm shopping on the website, if I see the color picker is square, I want it to be square for every product; if I see it is a circle, I want it to be a circle for every product, and there shouldn't be an oval mixed inside.

Here is my testing report. I have written a 24 pages Word document and moved it into Figma. I optimized the layout and labeled each issue to make them clear and easy to read.

Here is client’s review.