The death of archduke Francis Ferdinand of Hungary was the initial cause of ww1. However there was a build up to ww1. Countries had new powerful weapons and wanted to capitalise on this. The navy’s of many countries were being expanded. Political disagreements between countries led to increased tensions.
Yes, The birth rate of most of Europe has slowed greatly and with instability in Africa and the Middle East has caused many refugees to flock to the stable and economical prosperous Europe.
In 1529, Martin Luther and Ulrich Zwingli met at the Marburg convention to bring together Protestant factions.
They disagreed over how reformation of the Catholic Church was possible. Luther believed the ability to reform laid in the gospel and convincing people to change based on the teachings in the gospel while Zwingli wanted to use political means to force changes.
The 4 main causes of the Great Depression were the stock market crash of 1929, bank failures, overproduction, and drought.
So, for your question, Overproduction in factories and unpaid bank debts
