Even though my upload speed is good (Tested on speedtest.net)

It still takes forever to upload my game

When I test I get a speed of around 6/10 Mbps Upload

Is there any known reason for this?

Any ideas if its something that I can fix?

Thanks!

Due to the pandemic lockdown going down all over the world, a lot of ISPs are throttling overall up/down speeds across their networks. This is because everyone is at home social distancing right now and the best way to communicate is by internet, so there is a strain on the infrastructure. Be patient. If & when we survive this medical crisis, and most people return to work, the overall internet speeds will return to normal.

Minor edit: I have experienced the same problem. You're not alone.