Complex sentence: After the Ming Dynasty, which they considered itself 華, a cultured civilization was collapsed under the Qing from Manchuria, which was considered 夷 in 1644, the Ming was thought of as the last of the true Sino culture (中華).
Split into simpler sentences: After the Ming Dynasty, which regarded itself as "huá" (華), cultured civilization was considered to have collapsed under the invasion of the Qing from Manchuria, who were considered barbarian (夷) in 1644. The Ming was thought of as the last true Sino culture (中華).