how long is the great wall of china and why is it not given exactly whom made it??

Today, the Great Wall stands only approximately 5,500 ft long (8,851.8 km) (according to a study in 2009) but later studies show it was probably over twice that length in ancient China. It's length decreases day by day because of erosion. Hope that was helpful!
Sources (and more info): https://www.travelchinaguide.com/china_great_wall/facts/how-long.htm