Past Perfect
для действий, которые произошли до другого "прошлого" действия
для действий, которые запланированы перед установленным временем в прошлом
для действий, которые закончились в прошлом и результат был виден в прошлом
можно использовать Past Perfect с before и after без разницы в значении
МАРКЕРЫ
1
before
after
already
2
for
since
just
3
till
untill
when
4
by
by the time
never
They had already reserved the table when they went to the restaurant 
They had already sat down for dinner by 8 pm. 
She left after she had finished her work 
She left after she finished her work 
Bill had injured his legs in a car accident, so he had to use a wheelchair for six month
