Past Perfect Simple
USE: We use the past perfect simple for actions or situations that finished before another action, situation or time in the past
AUXILIARY VERB USED TO MAKE QUESTIONS: Had
STRUCTURE: Had + past participle
EXAMPLES 1: Juana had finished the cake before Thomas arrived home.
EXAMPLE 2: Hundreds of people had visited the Mona Lisa in the last 10 years.
ADVERBS OF TIME: before - After - when - already - for - for a long time - for ages - just - never - once - so far - yet - since 2007/ June
Past Perfect Continuous
USE: For an action that started in the past and were still in progress when another action started or something happened.
USE 2: For actions that were in progress in the past and had an effect on a later action.