1. There isn't a bookshelf in my room

- THERE IS + Danh từ số ít + Trạng ngữ (nếu có) 

2. The computer scree is in front of the dog

- in front of : đằng trước >< behind : đằng sau

3. My favourite subject is English

- English là một môn học nên là subject 

- My favourite + S + is/am/are + .... ?

4. Phong lives with his family : his parents, his little sister.

- Thì HTĐ : S + Ves/s

- Phong là số ít nên + Ves/s

5. I am a student at Cau Giay Primary school.

- Thì HTĐ dạng tobe : S + am/is/are + N

1, There is a bookshelf in my bedroom

$⇒$ There is + danh từ số ít

2, The computer screen is in front of the dog

$⇒$ S1 + tobe behind + S2 = S2 + tobe in front of + S1

3, My favourite subject is English

$⇒$ S + like(n.) + N + best = Sb's favourite N + tobe + N

4, Phong lives with three people: his parents, his little sister.

$⇒$ Do bốn người thì bao gồm cả Phong nên khi chủ ngữ là Phong sống cùng với thì phải trừ Phong ra là 3 người

5, I am a student at Cau Giay Primary School

$⇒$ S + study/ studies + at + trường = S + tobe + a student at + trường