In order to translate the category and description. Please follow the steps -
For category -> Go to community >> Languages >> Manual translate >> Choose the language from the dropdown >> under System and Logo >> Scroll down to categories and change it.
Refer to screenshot: https://app.screencast.com/GE5bo1s60c9FM
For Description -> Go to community >> Languages >> Manual translate >> Choose the language from the dropdown >> Navigate to Portal >> select Topic Description and change accordingly.
Refer to screenshot: https://app.screencast.com/E1hpU5SNQ0Evs
Refer to the help file: Manage Community Languages