The Description Editor tool of the Theme Tweaker add-on allows you to edit full and brief product and category descriptions directly in the storefront. Hence you can use it to add a description of a product or category in another language or translate an existing one if required.
For this purpose:
In the storefront, locate a product or category you need to edit and open the product or category details page:
Switch the storefront language to the target language of your translation:
Edit the required product or category description using the Description Editor tool as described here:
Save the changes.
That’s it! The product/category description will now display in the required language when the language is switched.