Imac Super Slow

From what I can tell, you have three main problems with your Mac.

The first problem is a hardware limitation- you have an 5400 RPM HDD in your computer still. It's recommended that you swap it out with an SSD if possible, as this will do wonders for your computer's speed.

The next is the multiple anti-virus/cleanup apps you have installed. You have both CleanMyMac and AVG. Both are unnecessary (and at least one is downright harmful). You should uninstall both right away, as they're only making your computer slower. Instructions from MacPaw to uninstall CleanMyMac can be found here. Instructions to remove AVG can be found here. Do not just move them to the Trash! If you do, many files will be left behind, as these apps deeply entrench themselves into your system.

You don't need anything but Apple's built-in security- you can read more about that here - Effective defenses against malware and other threats - Apple Community

Finally, the adware you have installed. Delete the each of the files listed below-

~/Library/LaunchAgents/com.onlineapplicationstatus.AppStatus.plist

~/Library/Application Support/AppCommon/AppStatus --protect

~/Library/LaunchAgents/com.appactivity.AppActivity.plist

~/Library/Application Support/AppPolicy/AppActivity -i -c 748931 -isn 9521E8A7-CD92-4532-B67A-9E32624EC396

After doing so, restart your computer in Safe Mode, then download and run the free version of Malwarebytes. Malwarebytes is the only generally trusted anti-virus, and should find any more adware or remnants of your "anti-virus" and "clean-up" softwares. After doing what it advises, please run EtreCheck (with full disk access) again and post it here. To give EtreCheck full disk access, simply go to System Preferences > Security and Privacy and allow it from the list of apps. Note that this cannot be done if you got it from the App Store- if you did, delete it and get the official one from the website, which can be found here.

Depending on the report you post, a wipe and selective restore may be necessary.

Your computer is a mess.

The best antivirus, cleaning app, and overall maintenance app for Mac OS is Mac OS itself. All you need to do with Mac OS to keep it secure and running well is to keep it up-to-date and do periodic (about 1x per week) restarts. Other than that, leave it alone. Adding third party antivirus, cleaning, security and other types of maintenance apps to Mac OS adds no additional level of security. The only thing these apps do is have the opposite affect users want. They make Mac OS slow, unstable, generate odd behavior (much like you are experiencing) and make Mac OS appear buggy. 

Please locate the developers uninstall instructions for CleanMyMac AND AVG and follow to the letter. Then restart in Safe Mode per the directions in Use safe mode to isolate issues with your Mac and then restart normally. 

Then install Malwarebytes and use it to remove the adware that has been installed on your computer.

This is also a big problem at the heart of the matter:

Hardware Information:

iMac (21.5-inch, 2017)

iMac Model: iMac18,1

2.3 GHz Dual-Core Intel Core i5 (i5-7360U) CPU: 2-core

That is the crippled and slow educational/institutional iMac. Entry-level consumer iMacs that year had a 4-core 3.0ghz processor and, even with the slow hard drive issue, were 50% faster in benchmark tests than yours:

Geekbench scores are from the MacTracker™ database, available free in the Mac App Store.

Your only cost effective option for improvement is an external SSD in a USB3 enclosure set as the boot volumes. Your drive's data transfer speeds are currently 60MB/sec and under; the external SSD solution will bump that to about 400MB/sec. That will give a very palpable improvement in your computer's usability.

Due to cost and the construction of the iMac case, swapping the internal drive is severely cost ineffective. It requires expensive professional opening of the sealed case and would only be slightly faster than the external SSD option, which is within the capabilities of the average home user.

Also, when you move to another computer, the external SSD drive can still serve for backups there. The expensive internally swapped drive option? It usually goes to the recycle bin with the rest of the computer