I see some issues in your report. First is you have CleanMyMac installed which is considered malware by most experienced users on these forums. Mac OS is catlike in that it cleans itself, Mac OS does not benefit from nor does it require any of the following types of apps:
· Antivirus Apps
· Cleaning Apps
· Security Apps
· VPN Apps
· Maintenance Apps
What these types of apps do is the exact opposite of what users want. They make Mac OS slow, appear buggy, can damage Mac OS and sometimes create unwanted behaviors. In short, they are really bad news!
So the first order of business for your computer is that you need to locate the developers. uninstall instructions for CleanMyMac and please uninstall CMM. Because CMM is pretty nasty stuff it tends to leave parts behind after being uninstalled, a testimony to how poorly written the app is! To fully ensure you have uninstalled it please download the free version of FindAnyFile directly from the developer. Then have it search your system for the following:
Have it Trash any files with those names in them and then ensure the Trash is empty.
Next, there is an indication that the hard disk portion of your Fusion Drive is slow. That can be due to your Fusion Drive either failing or it may have become unfused. If it has only become unfused then it can be re-fused. Apple explains how to do this in How to fix a split Fusion Drive - Apple Support
If the HD is failing then I'd recommend simply replacing the computer as it is now obsolete, parts are tough to obtain and well a new Mac will dramatically improve performance! You can check to see if the HD is failing by downloading the free version of DriveDX and test the hard drive, not the Fusion Drive just the hard disk!! If ANY errors appear that means the HD is failing.
If the HD is failing, there is a final option you can do if you do not want to replace the computer. You can remove the Fusion Drive from the equation and add an external SSD. Doing so is a little challenging but if you follow the directions in the link below they work just fine:
Please follow the steps in How to setup an external SSD as your startup disk. The external SSD I recommend is the https://eshop.macsales.com/shop/owc-envoy-pro-sx , in my opinion this is a higher quality and faster drive that the one recommended in the setup instructions.