How to Build Ecommerce Websites, Best eCommerce Sites, best web design

Which site design to choose, what is the difference and what is better. Most often we look at the site on different devices and do not think whether it is adaptive or not, it's rubbery or static. The main thing is that it was convenient and everything was fullfreddy and full of usability. But, when the topic of website development becomes urgent, many questions arise. And it's good when you can tell the professionals in the field of creating sites, but still it would be nice and to figure out what's what for.