Imac slow response to mouse click.

Welcome to Apple Support Communities.

I believe we need to proceed with an EtreCheck report. EtreCheck is a useful App to diagnose and identify issues, both hardware and software. It is trusted by many users. Please follow the steps outlined below:

1. Navigate to: https://etrecheck.com and get the free version of EtreCheckPro.
2. Download it. It is a free and trusted app. It is often recommended here on Apple Support Communities. 
3. Open EtreCheck, and before running the report, be sure to check “Allow full Drive Access” at the bottom of the EtreCheckPro window.
4. Run the report, and put it in a post, as seen here: https://discussions.apple.com/docs/DOC-250000211. We will then examine the report for issues in your Mac.

-Jack

Please post the EtreCheck report following the instructions here: https://discussions.apple.com/docs/DOC-250000211.

Regarding the questions:

1. The Time Machine drive must be plugged in.
2. No.
3. No; Flash is a dead technology now.

Also, delete Bitdefender.

Jack

An Aside from your issue under discussion - Profile showing Big Sur 11.2 which is way out dated. Thee is an 11.4 available to fix various bugs in earlier versions and fixes Security issue. If already installed - please disregard.

There could be a number of reasons why this is the case. I suggest that you start by running an EtreCheck report, and optionally, posting it here if you need assistance with interpreting its results. EtreCheck is a diagnostics tool that comes in very handy to troubleshoot issues like this.

Ref: https://discussions.apple.com/docs/DOC-250000632

Update - today I can access EtreCheckPro from either Chrome or Safari. Yesterday's scan showed Adobe Flash Player installed, hard drive slow and no Time Machine found. I uninstalled Adobe, ran Bitdefender and did a back-up on my G-Drive. Today I ran another EtreCheckPro scan with my G-drive plugged in, and scan found no major issues!

My questions

• can you recommend a good link or way to use Time Machine for back-up, even when external hard drive is not plugged in?
• do you recommend clearing cache on Safari, or clearing history? Or some version of that?
• do I need to install any other app to open files in the absence of Adobe Flash Player? Recommendation? Or is this automatically taken care of somehow. Thanks!

I got the free version of EtreCheckPro, downloaded and ran it, and found I had Adobe Flash Player installed on my mac, a 'security threat', so I uninstalled it and checked library for related files. I wanted to run EtreCheckPro again, to check that it was cleared, and now my computer tells me it can't be downloaded - error 47 - there is no application to open it. I tried control clicking the app in downloads folder to override security - same message comes up. What do I do? Thanks.

Report also said I had no Time Machine backup. I just ran my external hard drive, but I don't keep it plugged in. What do I need to do to have Time Machine backup? Thanks so much.