How do I remove a yellow hovering window on iMac?

Typing in all Caps is the same as shouting at people.

That is part of Logic Pro's q-bat guide.

see > turn off logic pro guides

and > logic pro tutorial

Please post at least a screenshot of the problem and basic information about the iMac such as the model year, version of Mac OS and specifically how it’s configured. iMacs have been in production for over 25 years in hundreds of configurations and versions of Mac OS, we have no idea what you have.

Your question as it is posed is akin to someone sending a letter to a doctor and saying I don’t feel good what’s wrong?

You might try setting the minimum font size larger in Safari's Advanced settings pane:

Also it's nice to know I'm not the oldest here. You're at least 5 mos and 23 days older than me. Sometimes it gets tiring carrying that burden all the time. 🤣

No problem. FWIW I'm an old guy too..

In that second link that I posted, there are some good Logic Pro tutorials.

+1 👍