Q: El Capitan does not upload

if you posted from the computer with El Captain it did in fact upload.

see this article

Recommended settings for Wi-Fi routers and access points - Apple Support

check your computer for any 3rd party utility that cleans, keeps, snitches, sharks or otherwise "enhances" your OS X abilities and remove them as the developer instruction on their web pages, simply dragging to trash does not remove these apps and many of them cause interference with the normal operation of os X. Do the same for any Mac Anti-Virus solution for the same reasons. If you don't know what you have on your computer you may post an etrecheck report for further analysis.

www.etrecheck.com

past that you may need to contact your ISP to see if they intentionally throttle connections.