Slow Uploading depends mainly on the speed of internet connection and amount of data transferred. The actual speed of a connection is not what is stated, for example, DSL 128 is the potential download speed of the connection, which is 128 kilo bits per second (Kbps). The actual speed will depend on traffic over the network. You can test your bandwidth by referring to Test Your Internet Connection Speed, however it will not give you correct results while GBM is uploading your file.  If you wish to calculate an estimate time (not as accurate as testing the connection speed) you can refer to the following Calculator