The internet slowdown is really odd, I don’t have any issues with that whatsoever. But it could possibly be caused by UE4 using up resources, making other apps run slowly, which can make it seem like the internet is slow when really it is the program.
Go to Edit - > Editor Preferences and select the Miscellaneous tab, there will be a setting named “Use less CPU when in background”. Make sure option is turned on. It makes a big difference when using other programs with the editor open.
See if that helps! 