Hi @birzu_cristian
Create a "Best Selling" named attribute by navigating to Stores -> Attributes -> Product.
While performing, there will be an option on the left-hand side block saying "Storefront Properties" and clicking on that, you will discover one setting called "Used For Sorting in Product Listing". Once you find it, please set it to "Yes".
When enabled, again navigate yourself to the category page and you will find that attribute under the Display Settings configuration of "Available Product Listing Sort By" setting as well as "Default Product Listing Sort By" setting.
Hope it helps!