`1.` This is the first time I have eaten this kind of food.

`-` "before" `->` Chưa từng ăn trước đây `->` Đây là lần đầu tiên ăn 

`->` This is the first time + S + have/has + (ever) + VpII + O 

`2.` How long have you learned English? 

`-` Cấu trúc: When + did + S + V-inf + O?

`->` How long + have/has + S + VpII + O?

`3.` It's long time since we became close friend. 

`-` Cấu trúc: It's + time + since + S + (last) + V-ed/V2 + O: Đã...kể từ khi...

`4.` We haven't seen her since Chistmas Day.

`-` Cấu trúc: The last time + S + V-ed + O + was + time (trong QK)

`->` S + haven't/hasn't + VpII + O + since + mốc thời gian/for + khoảng thời gian: Đã ko làm gì bao lâu rồi..

`-` Christmas Day - Ngày Giáng Sinh `->` Mốc thời gian `-` since. 

 1,I haven't eaten this kind of food before. 

=>This is the first time I have ever eaten this kind of food.

It/This is the first/second,…time + thì hoàn thành

"before" → Chưa từng ăn trước đây→Đây là lần đầu tiên ăn 

2,When did you start learning English?

-->How long have you learnt English?

How long + have/has + S + VpII + O?

3,

 -->It’s a long time since we became close friends.

We have…become close friends for a long time……

 It's + time + since + S + (last) + V-ed/V2 + O: Đã...kể từ khi...

4,

The last time we saw her was on Christmas day

-> We haven't....seen her since Christmas day......

 S + haven't/hasn't + VpII + O + since + mốc thời gian/for + khoảng thời gian: Đã ko làm gì bao lâu rồi..

Cấu trúc: The last time + S + V-ed + O + was + time (trong QK)

                                                  #𝙏𝙏𝙉 𝙭 𝙉𝙋𝙏