Catalina slow

Please determine if the same problems occur in "Safe Mode": Use safe mode to isolate issues with your Mac.

I have has exactly the opposite experience where my Macs actually seem to be a bit faster and much smoother with Catalina. Maybe if you follow the suggestion below and post an Etrecheck report we might be able to help you.

I suggest you use the program created by Etresoft, a frequent contributor.  It will provide a snapshot of your system which we can analyze to possibly determine the cause of your problem. Please use copy and paste as screen shots can be hard to read. On the screen with Options, please open Options and check the bottom 2 boxes before running. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown.

https://itunes.apple.com/us/app/etrecheck/id1423715984?mt=12

Use the Add Text button to include the Etrecheck report in your reply.

Great! Thanks for the update.

She had you perform an SMC Reset:

These symptoms might mean that an SMC reset is necessary:

• ...
• Your Mac performs unusually slowly, even though its CPU isn't under an abnormally heavy load.

That was followed by the "Safe Mode" startup, and finally restarting normally. All of that is justified for a Mac that is performing slowly.