imac spinning ball

First, just so you know you've got the slowest Mac Apple offered at the time of purchase: 8 GB RAM and a 5400 rpm hard drive. It doesn't take much to slow it further and you've done that with installing CleanMyMac which is considered by most around here to be akin to malware.

There is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

So uninstall CleanMyMac according to the developer's instructions.

The report finds your drive speeds rather slow:

Write speed: 43 MB/s

Read speed: 43 MB/s

You can't upgrade the memory but there is something you can do about the drive's speed. You could get an external SSD, clone your boot drive to it, and boot and run from it. Typical read and write speeds from such a drive are around 10x faster, both in read and write, than what you're experiencing now.

If you decide to go that route I recommend contacting OWC (MacSales.com) Customer Support and have them recommend which of the many options they offer would be best for your particular iMac and your budget.

Please stop using the computer immediately! The hard disk appears to be failing and you have no backup from what I can tell. This means if the HD fails all of the data stored on the computer will be lost!!!!!!!!!!! This is critical and means the #1 priority is to backup the computer before the HD fails. Please buy yourself an External Hard Disk such as a OWC Mercury Elite Pro )2TB model) and backup the computer using Time Machine. If you don't know of Time Machine it is pre-installed on the computer and you can learn how to use it in Back up your Mac with Time Machine.

After the computer has been backed up, then you need to address the failing HD. My recommendation on a base model 2017 21.5" iMac is to simply replace the computer. The backup External Hard Disk can be used with the replacement Mac and also can be used to migrate your data from the old Mac to the new one by following the instructions in Setup Assistant and Migration Assistant.

Finally, you have CleanMyMac installed, which is a major NO NO. It does nothing to help your Mac and should be uninstalled. These forums are full of stories of CMM users that have made a mess of their computers by using this worthless app. Moving forward, Mac OS does not need any third party antivirus, cleaning, VPN, or ANY other third party maintenance apps!!

The spinning ball only means the computer is busy doing something. I would suggest that you do the following so we can take a look and see if there is anything wrong with what has been installed and what may be causing the Beach Ball (spinning ball) on your system.

It will help us get a good idea of what is causing your problem if you provide a report of your system, that way 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

Here's how to save and add the report to your reply in this topic:

Copy the report

and use the Additional Text button to paste the report in your reply.

Please re-read the instructions on how to attach it, they work. You have to save the EtreCheck report as a file (put it on the Desktop) and then copy the file.