Short answers, pulled from the story.
The Holy Roman Empire was founded at the turn of the 9th century following the coronation of Charlemagne by Pope Leo III. This entity sought to unify a fragmented continent under a single Christian banner while facing constant challenges from distinct national identities and competing powers.
Otto von Habsburg organized the Pan-European Picnic on the 19th of August 1989. This event broke the bracket of the Eastern Bloc and allowed tens of thousands of East Germans to flee to Hungary, setting in motion a chain reaction that led to the fall of the Berlin Wall and the end of communism.
Jews constituted 9.5% of the Polish population in 1933. Poland and Lithuania had the largest Jewish populations in Europe as a percentage of their total populations before the Holocaust depopulated many of their centuries-old settlement areas.
The number of inhabitants in the Kingdom of Bohemia decreased from three million to only 800,000 after the Thirty Years War. This demographic collapse resulted from the Bohemian Revolt where many Czechs were killed, executed, forcibly turned into Roman Catholics, or emigrated to Scandinavia and the Low Countries.
43.8% of the German population declared that they had no religion in 2022. Germany is one of the countries in Central Europe with a sizeable atheist and non-religious population alongside the Czech Republic and Switzerland.