Hi, what do you mean by "sessions"?

Do you mean that unwanted tabs are opening, either at startup or as you browse? Are they sites you previously viewed and closed, or are they unfamiliar sites (e.g., advertising)?

Or do you mean that as you open tabs, Firefox spins up for firefox.exe processes in the Windows Task Manager? Firefox is a multiprocess application which divides tabs between multiple content processes. You can reduce the number of content processes (this can reduce the number of total processes from 7 to 3). See: Firefox's performance settings.

Firefox is my default browser. When it opens there are a number of sessions open when I check with Task Manager. All are using memory and at times using CPU time. I tried to open each session from Task Manager but nothing showed up so can't tell if from previously viewed sites.

Yes, it's normal to have multiple processes. If you look at the Details tab and add the Command Line column, you'll see several that indicate -contentproc which are spun up to isolate and load balance different content. If you want to reduce the number of content processes, see the second part of my previous reply.

I followed the instructions you advised in Firefox performance settings and set the limit to 2. There are 5 sessions open. This didn't seem to change the open sessions. Do you have any other suggestions or do we just live with the 5 to 7 sessions running. Thanks

If you select 2 content processes, then after you exit Firefox and start it up again, I would expect you to see three or four total processes in the Task Manager during your next session.