Have an iMac (2015) with problems

In mid September I purchased a program titled CleanMy Mac which was advertised on Facebook.I had some installation problems and became suspicious of the program so I decided to dump it. I uninstalled the program seemingly effectively as all references disappeared. However I can no longer open Security or Accessibility and the machine now is operating very slowly

Mia Green

Hello, thank you for using Howly. I’ll be happy to help you out! May I ask your name?

Customer Replay

*****

Mia Green

Nice to meet you, *****!
What troubleshooting have you done so far?

Customer Replay

Yeah, me too.

Mia Green

😊

Customer Replay

Very little. The slowness began shortly after I installed the program and the inability to one Security etc was only noticed 2 days ago.

Mia Green

Got it, thank you. Could you please tell me what happens when you try to access Security?

Customer Replay

Message appears that the machine is unable to access the program. No reason or offer of reports.

Mia Green

I see, thank you!
Try booting into Safe Mode. Shut down the computer and then power it back up. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot-up is significantly slower than normal. This does some maintenance routines, and 3rd party applications don't load.

Customer Replay

Mia Green

Let me know once you're done

Customer Replay

Thanks Mia. I changed my Apple ID password earlier but I am unable to open any locks to change passwords.

Mia Green

Do you get any error messages?

Customer Replay

No. Have tried several passwords going back a while but the message vibrates a little and then just sits there

Mia Green

Got you
Please, follow the instructions below:
Select "Security & Privacy" from the "System Preferences" window. Select the "General" tab, and select the lock in the lower left corner to allow changes. Enter your computer username and password, then select "Unlock."

Customer Replay

Ok. that worked

Mia Green

Perfect!
Is there anything else I can do for you today?

Customer Replay

No. Thank you very much.