How did European nationalism and orientalism inform the attitudes and actions of Europeans in their colonies in the 19th century?

In answering this question, it is helpful to first consider a few important points. Specifically, the notion of “nation-state” is rather new and did not emerge until the nineteenth century. Prior to the nineteenth century, European territories were mostly multi-ethnic empires and kingdoms (e.g., Austrian Empire, Russian Empire, Kingdom of France, etc.). In the nineteenth century nation-states began to emerge and with them a strong sense of nationalism.
A good example of this is Germany, which was comprised of many small dynastic states and territories prior to 1871. In 1871, the German Empire was founded, which represented the first nation-state on German territory. The founding of the German Empire led to the development of a strong sense of national identity and nationalism. In Germany, this meant that the country invested massively into its navy and military and tried to obtain colonies in Africa and Asia. Germany saw itself as competing directly with other European nations such as Great Britain and France over world domination.
Closely related to nationalism and colonial possessions is the notion of orientalism (see Edward Said’s 1978 book by the same name). The term orientalism signifies an ideology that emphasizes differences between European culture and the culture of people in the orient. More importantly, embedded in this ideology is the notion that Western culture is inherently superior to the culture of the orient. These broad assumptions about the superiority of Western nations were then used as a pretext to occupy and exploit colonial territories in the orient as well as Africa. European nations fueled by nationalism competed against each other to seize territories in the Middle East, Africa, and Asia; and they felt justified in doing so because of their belief in their own superiority. This also meant that European colonial masters treated native peoples living in the colonies with little regard for human rights. Native peoples living in colonies were exploited, forcefully resettled, or enslaved by their colonial masters.