ثُمَّ يُوتِرُ بِهِمْ
Translation: Then the imam leads them in witr.
The word thumma establishes the preferred sequence: tarawih after Isha followed by congregational witr. Witr remains separate from the twenty tarawih rakahs.
This is the preferred congregational sequence, not a declaration that every tarawih performed after witr is invalid.