Short answers, pulled from the story.
Germanic paganism was the traditional religion of the Germanic peoples, practiced across Scandinavia, the British Isles, and modern Germany for at least a thousand years. Written sources for it span from the first Roman accounts to the final conversion of Germanic peoples to Christianity.
The four gods most securely attested across the early medieval Germanic world are Tiwaz (Tyr), Thunraz (Thor), Wodanaz (Odin), and Frijjo (Frigg). Their names survive in the days of the week: Tuesday, Thursday, Wednesday, and Friday respectively.
The chief Roman-period source is Tacitus's Germania. Later sources include Bede's Ecclesiastical History of the English People (c. 731), the Prose Edda attributed to Snorri Sturluson (13th century), the Poetic Edda, and the 10th-century account of the Arab traveler Ahmad ibn Fadlan. Most textual sources were written by outsiders, not by pagan practitioners themselves.
Germanic beliefs about the afterlife included an underworld (Hel, described as cold, dark, and northern), a warrior's paradise (Valhalla, a hall in Asgard), continued existence in the grave, and reincarnation. Beliefs varied by time and place and could be contradictory even within the same community.
Ragnarök is a Norse myth about the end of the world, in which a war between the gods and the forces of chaos leads to fire and the destruction of almost all gods, giants, and living things, followed by a rebirth of the world. An Old High German word, Muspilli, probably meaning 'world conflagration', suggests a related end-of-world myth existed in southern Germany as well.
Celtic influence is visible in the name of Thor (identical to Celtic Toranos/Taranis), the Germanic word for runes (from Celtic runa), and the word for sacred groves (*nemetaz from Celtic nemeton). Roman influence came through Interpretatio Romana, in which Germanic gods were worshipped with Roman names; this process also ran in reverse, embedding Germanic god names into the days of the week.