I'm giving a presentation in my German class. If I'm speaking about historical events, should I use the simple past tense or the past participle with an auxiliary verb? Thanks :)
In a historical presentation, you should usually use the simple past:
Das Deutsche Reich wurde 1871 begründet.
Using Perfekt would make it sound somewhat as if this had been just the other day, and as if it might still be around, both of which are wrong.
It's true that in colloquial speech, the Perfekt is preferred, but you're not chatting colloquially about recent events, you're going to be presenting about historical events. Those are two strong factors for preferring the simple past.
I have not seen any practical usage of the simple past tense (hatte, sprach, ging, machte) in everyday German. It is also called "narrative past" and used more in written (books, newspapers) German, while the present perfect tense (hat gehabt, ist gegangen, habe gesprochen, haben gemacht) is used more in conversational German.
If the presentation is important to you, you can watch a German documentary about a historical event, you can note what the narrator says there and imitate it in your presentation.