`1.` You should live in this mega city because it is noisy and polluted

`-` It is adj for sb to do sth: Nó thì như thế nào đấy cho ai đó để làm gì

`-` Should/shouldn't + V-bare: Nên/không nên làm gì

`2.` I have learned French for two years

`-` S + started + V-ing + khoảng thời gian + ago

`=` S + has/have + PII + for + khaongr thời gian

`3.` Jim started to maitain a healthy body mass index through regular physical activity since he was ... years old

`-` when $\approx$ since: khi $\approx$ từ khi

`4.` In view of the fact that accidents regualarly happen on such rainy days, you had better stay indoors

`-` had better = should + V-bare: nên làm gì

`5.` You should keep your bedroom quite, dark and coold to improve the quality and quantify of your sleepo

`-` suggest (that) sb do sth: gợi ý ai đó làm việc gì

`-` should: nên