Hi,
Well, you have several things coming into play here.
The width of each element and the spacing between them in the listing is calculated automatically.
And there are several things on your website leading to this result:
- in the settings of your menu item, under the "category options" tab, you have set a margin of 10px. So 10px on each side of each product "box" is reserved for that.
- You have also selected "thumbnails" borders there. But your template's main css file has some CSS code for the thumbnail class used when you have that option configured:
monosnap.com/file/DnqKtZRYvQ0HxQKvL0DIPHIG7Yi3iU
As you can see, it adds a margin-bottom of 40px, which adds a big gap between the rows.
- You also have custom CSS added in which adds 15px on each side of the product "box":
monosnap.com/file/SWtSfSdCAdOavRM0EXKYbKJe46ANbi
So remove that margin-bottom from your template's CSS and set the margin to 0 in the settings of the menu item and that should already be a bit better.
Also, maybe moving the cart module on the left sidebar to give more space for the main area would go along way so that it feels less cramped I think.