Short answers, pulled from the story.
Germanic languages are spoken natively by about 515 million people, mainly in Europe, Northern America, Oceania, and Southern Africa. English, the most widely spoken Germanic language, reaches an estimated 2 billion speakers in total.
All Germanic languages descend from Proto-Germanic, also known as Common Germanic. It was spoken around the middle of the first millennium BC in Iron Age Scandinavia and Iron Age Northern Germany.
The Germanic languages divide into West Germanic, North Germanic, and East Germanic. All living Germanic languages belong to the West or North branch, since the East Germanic languages, including Gothic, became extinct.
Grimm's law is a consonant change that shifted the values of all the Indo-European stop consonants in Germanic. Recognizing it, along with Verner's law, was a seminal step toward understanding that sound change is regular and toward building the comparative method of historical linguistics.
Crimean Gothic was the last East Germanic language to die off. It was spoken until the late eighteenth century in some isolated areas of Crimea, long after the Burgundians, Goths, and Vandals had been linguistically absorbed by their neighbors by about the seventh century.
The earliest coherent Germanic text that survives is the fourth-century Gothic translation of the New Testament by Ulfilas. He developed the Gothic alphabet for the work, which had previously been written with Elder runes.
English moved toward a largely analytic type because its strong initial stress steadily eroded unstressed endings, wearing away inherited inflectional morphology. Contact between Danelaw Viking settlers and Anglo-Saxons, plus Old French vocabulary after the Norman Conquest, also helped produce Middle English from the twelfth century.