If you can roll back this is the fix in fire fox to force multi threading, and FVD speed dial worked great, this new one is awful.
follow these instructions
If you're using Firefox 48 or later, you might be using e10s already.
Check about:support and look for a number higher than 0 in the
"Multiprocess Windows" entry. If you would like to opt-in, open
about:config and toggle browser.tabs.remote.autostart to true. On your
next restart, e10s should be active.
If you've tried enabling e10s following the instruction above, but your about:support
indicates that e10s is disabled (e.g., accessibility, add-ons can
trigger this), you can force e10s on for testing purposes. Within about:config create a new boolean pref named browser.tabs.remote.force-enable and set it to true. This is not encouraged, use it at your own risk!
Link to Wiki https://wiki.mozilla.org/Electrolysis
Customer support service by UserEcho