1.Because she was ill , she couldn't go to the party .

-> Because + S +clause , S + clause 

2. In spite of her sick,she insisted on going to work.

-> In spite of+ Noun/Noun Phrase/V-ing, S + V + … 

3. I haven't seen him since 1995 .

-> the last time + S + Ved/cột 2 + was + time => S + hasn't/haven't +Vpp 

4.Unless you don't take this letter to the post office , you will be late. 

-> V +O+or/otherwise + S + will + V(bare ) => Unless + S + trợ động từ ở dạng phủ định + V + S +will +V-inf 

5. We should eat a lot of fruit and vegetables every day .

-> It's a good idea + to V => S + should +V-inf

6.My bike isn't as expensive as yours .

-> S + tobe + not  +as/so +adj + as  +N/pronoun 

@Chaeyoung