Slow as molasis

It's not clear whether that's performance or connectivity issue, there are some things to try: Quick fixes if your Firefox slows down

I'd basically first try the same sites in Private Window, then restarting into Troubleshoot Mode from Help menu, eventually even crating a new separate profile to test.

If nothing changes, the next steps are to look into your security or antivirus suites, restarting/updating your routers etc.

Try making a new firefox profile and see if the same websites do load / run faster in the new profile (do not install any extension in the new profile)

If yes, then probably some extensions or settings are making your firefox slower.