problem with box quantity

-- url of the page with the problem -- : shop.petratoskefallonia.com

how can I increase the size of the box quantity

Hi,

Please see www.hikashop.com/forum/product-category-...ntity-box-width.html

And in the documentation:
www.hikashop.com/support/documentation/1...the-display.html#css
www.hikashop.com/support/documentation/84-css-styling.html

The problem continues and the button as you can see I can not put it in the middle while I set it

there is some other way to bring them to the middle and the quantity of the product to look better

Hi,

The issue comes from the padding added by the CSS of your template.
You can potentially increase the width of the input with such CSS:
input.hikashop_product_quantity_field {
width: 45px !important;
}
You can add it as explained here:
www.hikashop.com/support/documentation/1...ize-the-display.html

Also, regarding the centering, the issue is that you're using the "image and description" layout in your menu item instead of "image and title" and your thumbnail size is too big.
You can change that under the "product options" tab of your menu item in the Joomla menu manager.

there is a way to put the button in the center of the box product?

Hi,

Sure. You can simply use such CSS on your website:
.hikashop_products_listing .hikashop_product_stock{
margin: auto;
width: 50%;
}