Subcategory grid changes

Hello, I have a website running OpenCart 2.3.0.2 with the Fastor theme. When any of the main category pages is opened, what appears is a page with a list of subcategories in a grid with images. Link for reference https://parketilazur.com/trisloen-parket. I want to align the subcategories in the center as well as to change the number of categories per row to 3. I've been looking through modules, settings, some template files and of course google, but so far I have had no luck with finding anything that could help me. Thanks in advance!

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