How can i order data by specific String Field

i have the following get method

  FirebaseFirestore.instance.collection('comments').limit(5)
        .orderBy('commentDate',descending: true)
        .get(const GetOptions(source: Source.server)).then((value){
          //outputs
          today
          yestrday
          oldest
          oldest
          oldest
           
       });

in previous method i am sorting comments according to the latest .

one of the fields is commentOwnerId : Lx33AN0RwDEWzO7T3xQV.

Perhaps the owner of the comment is not the most recent , However, I want to show it as a priority over the rest of the documents .

  FirebaseFirestore.instance.collection('comments').limit(5)
        .orderBy('commentOwnerId ',descending: true) // here i am stack 
        .orderBy('commentDate',descending: true)
        .get(const GetOptions(source: Source.server)).then((value){
          //outputs
          myComment (yesterday)
          today
          oldest
          oldest
          oldest
           
       });

i notice if the commentOwnerId field is Boolean instead of string value so it work as expected
but of course i cannot use Boolean since i need to chick if it was == my id or no then descending it to true if it was mine .

How could i handle it ?