imac 2019 is running slow

Not a lot to go on with your post.

As such, I suggest that you run an EtreCheck report, and optionally, post it here if you need assistance with interpreting its results. In case you are not familiar with EtreCheck, it is a free diagnostics tool, developed by a valued forum member, that greatly aides in troubleshooting difficult Mac issues.

Ref: Using EtreCheck to Troubleshoot Potential Mac Issues

+2, please post an EtreCheck report of your system. Your initial post reads like going to your doctor and saying I don't feel good and asking for a diagnosis. I don't know of any doctors that would hazar a guess without anything to go on.