Hi there, GrammaLo.
After reading your post, it appears that you're having difficulty viewing your Google Calendar in Safari on your MacBook Pro on macOS Catalina as well as an iMac. We're glad to help with this.
How to install Safari extensions on your Mac -- Since this is also happening only in Safari, there may be an extension you're using that's causing the issue.
Select one of your computers to work with, and turn off the extensions you may be using in Safari. Then see if you're able to view your Google Calendar events correctly. If it's working, turn one of the extensions back on and test. If the issue returns, turn that particular extension back on, and select the others one at a time to isolate the issue. Once you've worked through the extensions on one Mac, move to the other and use the same steps.
If you've isolated the issues to one or more extensions, uninstall it/them.
If your Apple wireless mouse, keyboard, or trackpad isn't working with your Mac as expected -- If an extension isn’t causing the issue, and this is happening on two computers, it may be that the Apple Magic Mouse isn't tracking correctly. The steps in this section of this article can help.
Let us know how that goes.
Take care.
