Mojave Spinning Multi-Color Pizza of Death

If the problem appears to be isolated to Safari here are a few fundamental troubleshooting steps that may help. Some of the information will be redundant but review everything to determine if there is something you may have overlooked. Recommendations to remove all non-Apple "anti-virus" products remain.

• Safari is slow, stops responding, quits unexpectedly, or has other issues - Apple Support
• If Safari doesn't load a page or webpage items are missing - Apple Support
• How to use Internet plug-ins in Safari for Mac - Apple Support
• "Safe Mode": Use safe mode to isolate issues with your Mac - Apple Support. Determine if the problems exist in Safe Mode. Then, restart normally.

If you don't get anywhere, you can use the following procedure to determine if the problem is internal or external to your Mac. Causes may involve your router, your ISP, the DNS Server(s) it uses, or certain user-configurable options.

1. Shut down your Mac.
2. Load macOS Recovery by holding ⌘ and r (two fingers) while you start your Mac with a third finger.
3. At the macOS Utilities screen, release those two fingers.
4. Choose Get Help Online.
5. Safari will launch, but it will lack your bookmarks, favorites, history and other preferences.

Determine if the problem persists while using Safari in that mode. After that, restart your Mac normally, and reply with your observations.

Please determine if the same problems occur in "Safe Mode": Use safe mode to isolate issues with your Mac.

Needless to say, if you are using—or have used at any time in the past—any non-Apple "anti-virus", "cleaning", or "Internet security" junk, anything at all in that broad category of useless garbage, don't. A lot of things won't work if you do.

I don't use such things, don't have that problem on any of my Macs, therefore macOS is not its cause.

Assuming you want to fix your Macs uninstall it and determine if same problems occur in "Safe Mode": Use safe mode to isolate issues with your Mac.