Most of the time, the main reason for the slowing in upload speeds is your internet service provider (ISP). Some ISPs would often reduce it to give way to other users. So the best way to fix this issue is to contact your ISP.
What causes poor upload speed?
If you notice slow uploads, the most common causes are: Network connection is bad. Local Internet is slow. You have a firewall program that is blocking you.
Is 10 Mbps upload speed good?
Upload speeds of 10 Mbps or higher are generally considered fast internet speeds for upload because they can easily handle the common activities of the average user. For example, Skype recommends upload speeds of 1.2 Mbps or higher for HD video calling.