Slow iMac and constant crashes

You have many softwares running -- in addition to remove some unnecessary ones, you might also want to increase the memory (you have 2 empty slots available - 27" iMac has user accessible RAM slots).

Your report:

Free RAM: 57 MB

Used RAM: 6.47 GB

Cashed files: 1.47 GB

I think by adding at least another 8 GB (4Gb x 2) or 16 GB (8 Gb x 2) - can making things smoother.

If you want to take up this -- make sure to get your memory from reputable vendors, such as OWC or Crucial.

Uninstall CleanMyMac per their directions , Restart then run etrecheck again to see what chaff it left.

On CMM…

https://discussions.apple.com/thread/251370955?answerId=252661013022#252661013022

https://discussions.apple.com/thread/251442443?answerId=252814053022#252814053022

https://discussions.apple.com/thread/251464557?answerId=252841819022#252841819022

Hello,

You can save us asking dozens of questions by submitting a report from this App for us to look at…

EtreCheck is a FREE simple little diagnostic tool to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac. It will not display any personal info.

https://www.etrecheck.com/

Pastebin is a good place to paste the whole report if you capture the URL while there…

https://pastebin.com/

Whew, they've changed pastebin & made it harder, but after pasting in, click Create new paste button, then Embed button, then copy the URL...

<script src="https://pastebin.com/embed_js/KuvnghqA"></script>

The important part is...

https://pastebin.com/embed_js/KuvnghqA

Workable but harder for me to work with...the Note tool on the bottom of this editor's toolbar, as shown in the image, to copy and paste the output from EtreCheck. In a Reply before you click post, look for this to add longer texts...

Your Fusion drive is a little slow, and it may be getting full. Hard to tell from the report but it looks like you have very little free space (under 10 percent) remaining. Verify that with Disk Utility, or do "Get Info" on your startup volume:

I think a big issue is Chrome:

Top Processes Snapshot by CPU:

Process (count) CPU (Source - Location)

system_profiler (2) 45.90 % (Apple)

Google Chrome Helper (Renderer) (17) 41.76 % (Google, Inc.) <<<------

EtreCheckPro 25.72 % (Etresoft, Inc.)

WindowServer 15.62 % (Apple)

kernel_task 13.74 % (Apple)

Top Processes Snapshot by Memory:

Process (count) RAM usage (Source - Location)

Google Chrome Helper (Renderer) (17) 1.18 GB (Google, Inc.) <<<-------

system_profiler (2) 548 MB (Apple)

MATLAB 460 MB (? - /Applications/MATLAB_R2019b.app)

EtreCheckPro 411 MB (Etresoft, Inc.)

mdworker_shared (13) 175 MB (Apple)

Pulse Secure is unneeded security software, All those interfere with the protection for which you paid Apple a lot to build into the macOS. Follow the developers' instructions for full removal.

The only third-party utility I find unobtrusive and safe is MalwareBytes, for detection of adware. I run it in standalone mode.

Looks good, but as Samtenor says, you are running an awful lot for only 8GB, I only differ in that I'd at at least 16 GB of Ram...

https://eshop.macsales.com/shop/memory/iMac/Retina-5K2015/DDR3L

16GB more RAM should really help the speed.