Even though the byzantine empire fell in 1453 and was in decline for centuries before
that, it left a strong legacy behind. what was the most important contribution that
byzantine made to world history? why is that most important?

In my honest opinion , i’d say franklin d roosevelt was a president that impacted our nation , i say this because fdr is voted among top three best us presidents and he was the longest serving president by 3 terms , usually presidents only supposed to have two terms increments of 4 years , equivalent to 8 years total before election time. and he established the fdic , through the 1933 banking act and he established the us , social security system , during his presidency, and established a national minimum wage , through the fair labor standards act , fdr led the allied coalition to victory in wwii and he played a major role in the creation of the united nations.

Primary sources are usually  more accurate and are written by someone who experienced it or witnessed it. secondary sources are those who heard of it after the fact that can lose details and or twist the event in a light that benefits them.