$\text{1.}$ I think English is not as difficult as Chinese

=> So sánh bằng :

+ S + V + as + adj/adv + as + N/pronoun

+ S + V + not + so/as + adj/adv + N/Pronoun

$\text{2.}$ Alice is the oldest students in her class

=> So sánh hơn nhất :

S + tobe + the + adj _est / most _ adj

$\text{3.}$ Its a good idea for you to visit Ha Giang province in February

=> Be a good idea for sb to V : ý tưởng hay cho ai làm gì

$\text{4.}$ Robots may help people with the housework

=> May + Vinf: có lẽ làm gì

`@` $\text{anhanh}$

1. is not as difficult as Chinese

so sánh bằng: be (not) as adj as

2. the oldest students in her class

so sánh hơn nhất với tính từ ngắn: be the adj-est

3. for you to visit Ha Giang province in February

be a good idea for sb to V: ý tưởng hay cho ai làm gì

4. may help people with the housework

may + Vinf: có lẽ làm gì