The easiest way to create Google feed is to use a built-in Feed wizard. Please go to Catalog> Feeds Profiles and click the “Setup Google Feed” button.
You'll need to complete 7 steps. Please follow them one by one.
Category names that are selected in the mapping are supposed to be ignored and not included in the feed file. Their names won't be pushed into <g:google_product_category> tags. This won't affect products assigned to these categories; they'll appear in the feed file if the opposite is not configured via Conditions. With the help of category mapping, you can regulate which category name will appear for <g:google_product_category> if the product is assigned to more than one category.
For example, if a product is assigned to the categories “Clothes” and “Sales”, the extension will choose the category with the biggest value by default. In your case, it can be “Sales”. If you want to assign the product only for the “Clothes” category, select the “Sale” checkbox to ignore it.
If you want to manage a category that will be selected for the product in the feed by yourself, select the categories that you would like to ignore. In this case, if the product is assigned for more than 1 category, the extension will ignore the marked checkboxes.
Google Product category needs mapping which should be done when creating the feed via the built-in wizard. Your store categories need to be mapped in line with the Google taxonomy. Google taxonomy structure (categories tree) is available here.
To make the process more simple, please enable “Use Google Taxonomy Categories Names” and start entering the names according to the taxonomy. You will see the automatic pop-up hints with the suggested variants you can choose from:
Once this is done, the categories will match the google taxonomy and pass the validation.
However, please bear in mind that some attributes like GTIN or MPN need to be created in Magento 2 if they do not exist yet.
That's it. The feed profile is successfully created and ready to be generated.