Because you are asking about so many different topics, we can only give you relatively brief discussions of each topic.
Trench warfare is a term that is most closely connected to World War I, although it was practiced in other wars as well. This was a type of warfare in which both sides dug massive systems of trenches to be used as defensive positions. This, along with weapons technology, made it almost impossible for either side to gain much territory in an offensive. Trench warfare caused a horrible and bloody stalemate on the Western Front for much of the war.
Otto von Bismarck was the first chancellor of the unified country of Germany. He was in power from 1871 until 1890. It is Bismarck’s leadership that is generally credited with helping Germany unify. Under his leadership, the country became a significant power in Europe.
The Qing Dynasty was China’s last dynasty. It lasted for a very long time, holding power in at least a nominal sense from 1644 until 1912. The Qing rulers were not ethnic Han Chinese but were, instead, Manchus from northeastern China. The Qing Dynasty was unable to deal with the intensifying contact with the outside world in the 1800s. It was not able to modernize the country and make it more powerful.
The Meiji Restoration contrasts with the Qing Dynasty in an important sense. The restoration happened in the 1860s in Japan. Officially, it involved restoring the emperor to the position of power that he had once held. In reality, the main thrust of the restoration was to make Japan a more modern country. Under the Meiji Emperor, Japan went from being an isolated and technologically backward country to being a major world power.
The Great Trek was a large movement by Boer farmers in what is now South Africa in the 1830s and ‘40s. The Boers were the descendants of people (mainly Dutch) who had colonized the area. When Great Britain took control of the Cape Colony and started to remake it along their preferred lines (for example, by outlawing slavery, the Boers chose to leave. The Boers moved inland and set up a number of small new countries that would remain independent for varying lengths of time.