When do I use the present perfect, simple past and past perfect?

First of all, I'll give you an example of the same verb in those three different tenses, all in the first person singular. We'll use the verb "to read", or "lesen" in German.In present perfect we have: "Ich habe gelesen"The simple past form is: "Ich las"The past perfect form is: "ich hatte gelesen". Not that "hatte" is the simple past form of "haben", which we use for the present perfect. This indicates that it happened before something else and this is the exact use case: you use it to express an action in the past that had happened, before another action took place. Similarly, the present perfect is used to express an action, which happened in the past, but which focuses more on the result of the action now.The simple past, on the other hand, is used to express facts that have taken place in the past, such as "It was bad". It is usually used for reports or stories.