Plus-que-parfait

Question 1

uses of the plus-que-parfait

Answer 1

indicates an action that happened before another past action started (in english, had done)

Question 2

forming the plus-que-parfait

Answer 2

use the forms of avoir or être in the imparfait + the past participle of the main verb
eg. tu avais oublié l’anniversaire de ta meilleure amie