Hi colliermail, Firefox is a multiprocess application. In addition to the main process to run the program, there are multiple "content" processes used to load websites. You can restrict the number of content processes using a setting on the Options page. This article has more info:

Firefox's performance settings

I'm not sure why there would be so many processes if you only ever opened one tab, but maybe you opened and closed various tabs, and Firefox simply kept the processes running in anticipation that you would be opening more tabs. There definitely isn't a direct 1:1 correspondence between processes and open tabs like some other browsers.

By the way, the CPU and disk activity in your Task Manager is nearly zero, so Firefox being slow must be caused by something else. Is anything in the following article useful:

Quick fixes if your Firefox slows down

Did you previously open a lot of tabs in the Firefox session?

In that case it can help to close and restart Firefox via a button on the about:profiles page.

It is possible that Windows is swapping data to the page file.

You can also check the Firefox Task Manager (about:performance) and about:memory page.

• https://support.mozilla.org/en-US/kb/task-manager-tabs-or-extensions-are-slowing-firefox
• https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-ram