There are three past tenses: 1) Perfekt: This one is the most used one. let's say when we talk about what had happened in the past we would use this one, e.g. Gestern habe ich einen Film gesehen, dann bin ich spazieren gegangen. This tense is used for full verbs. 2) Präteritum This tense is usually used for modal verbs, 'haben' and 'sein', e.g. Gestern hatte ich keine Zeit, ich war zu Hause. But then, it is also used for written texts, e.g. a novel very likely will be written in it. 3) Plusquamperfekt That is a past tense in the past, it means when we are talking about something in the past, and one event had happened even before, e.g. Nachdem ich gegessen hatte, bin ich spazieren gegangen.

In German there are 6 tenses - 2 future tenses, the present and 3 past tenses. https://deutsch.lingolia.com/en/grammar/tenses