[Boaz]

The Conquest of Gaul and The Civil War by Julius Caesar, The Twelve Caesars by Suetonius, The Fall of the Roman Republic and Parallel Lives by Plutarch, and From the Founding of the City by Livy (Titus Livius) should all be available readily in multiple English and German translations. These books are from authors who were eyewitnesses or who lived soon after the events during the end of the republic and the beginning of the empire.

Also, Colleen McCullough has written a series of historical novels about Julius Caesar. I have not read any of them, but I've read positive reviews.