1)It is believed that she started the fire => She is believed........ 2)that sentence is not ........correct ( grammar)

1) It is believed that she started the fire.

⇒ She was believed to start the fire.

Câu chủ động: S1 + QKĐ + that + S2 + QKĐ.

Câu bị động: S + be + believed + to V(nguyên mẫu)

2) That sentence is not grammatically correct.

Trạng từ "grammatically" đứng trước tính từ "correct" để bổ nghĩa cho tính từ.