Why is it so slow uploadfile

Robert's right, there are various factors involved here, but generally the main contributor to how fast files can be sent back or forth is your Internet connection.

All of the Dropbox servers are located in the US. Your connection speed to Dropbox depends on the routing you get between your ISP and our servers, and may be slower than your ISP's rated speeds.

Sometimes resetting or retrying your connection gets you a different route and better speeds, but that is outside of our control. Some ISPs also throttle sustained connections so if you see an initial high connection speed followed by lower speeds, that could be the reason.