Get a faster client internet connection.
Uploads are always slower than downloads, typically 1/5 the speed at best. And large files take a lot of bandwidth.
Check the size of your file, check your upload speed and start by working out the best time you could get by
upload speed / (file bytes * 10) == seconds to transfer
- that';ll give you an approximate "best case" transfer, in practice it'll almost certainly be slower than that.
If your actual time is similar (i.e. between the best rate time and twice that) then you really can't improve upload without changing your connection.