Product & Categories 3 column (div) layout

Hi,

Can you provide a link to a page with the issue so that we can look at the situation ?

The issue comes from some customization.
You have the CSS:
.hkc-md-4 {
width: 33.66666566666533%;
}
in the customized frontend CSS of HikaShop. That CSS doesn't exist by default and that's this CSS which breaks the display since 33.6 * 3 is higher than 100% and thus it's not possible to have three elements of that width on the same line.
You'll have to fix your CSS and use something like we have by default instead:
.hkc-md-4 {
width: 33.33333333%;
}