3/ The plane took off before we arrived at the airport

-> By the time we arrived at the airport the plane took off

The plane took off before we arrived at the airport

-> By the time we arrived at the airport, the plane had taken off

4/ I would prefer you not mention this matter to anyone else

-> I'd rather you didn’t mention this matter to anyone else

5/ My sister failed to get into a college

-> Mys sister didn't succeed in getting into art college.

6/ Although he wasn't experienced, he got the job

-> Despite his inexperience, he got the job.

7/ After 8 year, studying abroad, he return home as a doctor of law

-> After he had been abroad for 8 years, he returned home as a doctor of law.

3/ The plane took off before we arrived at the airport

-> By the time we arrived at the airport, the plane had taken off.

4/ I would prefer you not mention this matter to anyone else

-> I'd rather you didn't mention this matter to anyone else

5/ My sister failed to get into a college

-> Mys sister succeed in getting into art college.

6/ Although he wasn't experienced, he got the job

-> Despite his inexperience, he got the job.

7/ After 8 year, studying abroad, he returns home as a doctor of law

-> After he had been abroad for 8 years, he returned home as a doctor of law.