It is suppose to have 4 running or more as Addons stick them in the Task Manager also. Is why called Quantum. https://www.howtogeek.com/332449/whats-new-in-firefox-quantum/ do this please : go to the Firefox 3 Bar Menu --> Options --> Privacy & Security panel and under Permissions check (put a tick in the box) the setting to Prevent Accessibility Services from accessing your browser. Monitor in Task Manager. Should stay below 2 gigs. If excessive then do below and monitor and change if need to...Test and go up again , go back down, it will eventually get a zone you and it can live with. Go the 3 Bar Menu then Options --> General --> Performance and untick everything. change the recommended size lower then see how it runs. Note: 1 = No Multiprocessor = slow again. Try 2 Restart Firefox after making these changes please. Please let us know if this solved your issue or if need further assistance.