past participle
ring
rung
John went to work.
Then Mary rang John's doorbell.
Mary rang John's doorbell but John had gone to work.
I hadn't bought a towel, so I couldn't have a shower.
I had not bought a towel
go
gone
I lost his number.
Then I was pleased when I got a text from Jim.
I was pleased when I got a text from Jim because I had lost his number.
The plane had left by the time I got to the airport.
The plane had left
lose
lost
I forgot to set the alarm.
then I woke up late.
I woke up late, because I had forgotten to set the alarm.
They passed the exam because they had practiced a lot.
They had practiced a lot.
bring
brought
They left the tickets at home.
They got to the station.
When ...., they realized
When they got to the station, they realized they had left the tickets at home.
You had studied Italian before you moved to Rome.
You had studied Italian