Imac is Slow

2019 4K iMac with 1TB HDD... the 1TB HDD drive that shipped as the standard configuration is known to create performance bottleneck with current versions of MacOS.

I'd suggest purchasing an external USB-C SSD, reinstalling MacOS onto that, and setting it up to work as your startup drive. Use an external storage device as a Mac startup disk - Apple Support

For a second opinion run Etrecheck and post the results.

No need to download dodgy 3rd party software. Please generate instead the system report as detailed in Get system information about your Mac - Apple Support. Scroll down to “View a System Report” and choose “See a shorter report” under point 3. To attach it to your reply, copy the report and use the Additional Text button for pasting the report in your reply:

We will need some additional information in order to get an idea of what is causing your computer to be slow.

It will help us get a good idea of what is causing your problem if you provide a report of your system, so we do not have to play 20 questions with you. The report we are requesting does NOT provide any personal information and is extremely safe to use. Please navigate to www.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again. 

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click How to use the Add Text Feature When Post… - Apple Community It is helpful to us if you download the report to your Desktop.