We use...
... a simple present perfect tense in sentences with this/it/that is the first/second/third/only/best/worst etc.
We use the past progressive to say that something was going on around a particular past time.
We can use the past progressive and simple past together.
Past progressive: longer background action or situation.
Simple past: shorter action that interrupted it or happened in the middle.
The past perfect tense is related to a moment in the past in the same way that the present perfect is related to the present moment, ie. it describes an action completed before some special past moment we have in mind.
The past perfect progressive emphasizes the duration of an activity that was in progress before another activity or time in the past.