The pluperfect is the ich hatte es getan or I had done tense. You make the pluperfect in German by taking the perfect tense (the ich habe es getan tense) and changing the auxiliary verb (the habe or the bin etc.) into the simple past version of itself (hatte or war etc.). So instead of ich habe ein Eis gegessen – I have eaten an ice cream you get ich hatte ein Eis gegessen – I had eaten an ice cream. And instead of ich bin im Ozean geschwommen – I have swum in the ocean you get ich war im Ozean geschwommen – I had swum in the ocean.
Basically, where you would use the pluperfect in English, you also use it in German. There's one exception to this though. Where you are referring to a situation that started in the distant past, but which is still ongoing at a point in the nearer past that you are talking about, although you'd use the pluperfect in English, in German you'd use the simple past. For instance: Since I had lived in Munich, I had been visiting him every Saturday = Seitdem ich in München wohnte, besuchte ich ihn jeden Samstag.
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