Annoying constant still picture

For now keep using the Mac in Safe Mode.

Certain functions do not work in Safe Mode. If you must restart normally, don't click the OK button in that "Completed" window quite yet. I don't know what it is, and you should not proceed with the installation of something unless it is expected, and you are certain you want to install it.

It is not a Safari window. It is merely the Safari icon, which is commonly used by malicious software to convince you it is legitimate. It means nothing in itself.

In an effort to identify what may be attempting to install, please open System Preferences > Users & Groups. Your User Account will be selected already. Click Login Items. Are any Login Items shown?

Login Items are explained in Open items automatically when you log in on Mac.

First, force your Mac to shut down by pressing and holding its power button, for up to 10 seconds, until your Mac turns off.

Then, restart your Mac in "Safe Mode": Use safe mode to isolate issues with your Mac. If it continues to appear come back here for further instructions.

Since you posted your last reply I have reason to believe the "installer" process shown in your initial screenshot is caused by something called "ValueKnow". You may find an app by that name in your Mac's Applications folder, or a Safari Extension, or both. If you do, uninstall or remove them respectively.

"ValueKnow" and things of its ilk (such as "Safe Finder" among countless others) is an example of adware, a broad category of malware that may have leveraged a phony "Adobe Flash Player update" to deceive you into installing it.

To learn how to recognize and avoid those threats please read:

How to install adware

Beware bogus Adobe Flash "installers"

Effective defenses against malware and other threats