Internet speed half on some sites but on some full??

[Hury__]

So, I have 10Mbps ADSL internet and while i downloading on Steam,Origin and other sites it acts like 5 Mbps internet but on other sites like Megasync, Mediafire etc.. it's has full speed(10 Mbps). Why?
Also i check my speed on "Speedtest.net by Ookla" it's say around 9.0 Mbps what is normal.

 

[Alabalcho]

Your ISP' links to Steam, Origin etc could be overloaded by other users like you.