Sure, here are the sentences rewritten using the present perfect tense:

1. Lan started to live in Da Lat 4 years ago.
➔ Lan has lived in Da Lat for 4 years.

2. My son began to study English when he was young.
➔ My son has studied English since he was young.

3. I have never eaten this kind of food before.
➔ I have never eaten this kind of food.

4. Lan has never seen such a beautiful girl before.
➔ Lan has never seen such a beautiful girl.

5. This is the best book she has ever read.
➔ She has never read a better book than this.

6. This is the first time Cuong went to China.
➔ Cuong has never been to China before.

7. My sister started learning 2 years ago.
➔ My sister has been learning for 2 years.

8. My parents began drinking when it started to rain.
➔ My parents have been drinking since it started to rain.

9. My brother last had his car repaired when I left him.
➔ My brother has not had his car repaired since I left him.

10. When did he have it?
➔ When has he had it?

11. I haven’t seen my grandmother for 6 months.
➔ I have not seen my grandmother in 6 months.

12. Tonny hasn’t taken a bath since Monday.
➔ Tonny has not taken a bath since Monday.