how to have this layout ?

Hi,

You want to create a menu item of the type "HikaShop products listing" via the Joomla menu manager (or use one you already have).
Under the "products options" tab of your menu item, you'll find the setting "sub elements filter". Set it to "group by category" and the listing of the products will be grouped by category, like you want.

Hi,

In that same tab of the same page, you'll find a setting "Layout type". It is set to "image and title" by default.
Change it to "image and description" to get the description.

Hi,

My bad, I thought you were talking about displaying the description of the products, not the description of the categories.
There is no option for the description of categories.
For that, you'll have to edit the file product / listing via the menu Display>Views.
There, after the line:

<h2><?php echo $category['category']->category_name; ?></h2>

<span class="category_description"><?php echo $category['category']->category_description; ?></span>