When I click CMD+B, I want the font to be BLACK instead of BOLD. How can I change it?
You can't. As it has been told in your other posts, you definitively should use styles. Until you do it, you will encounter these kind of problems.
I have not bothered to test this recently as I use paragraph and character styles to format my text as @jmlevy recommends, however...
In the "old days" using Cmd-B would take a light-style font and make it black. A regular-style font would become bold. Of course, this did not work on every font and, as I said, I have not tested it for a number of years.
Yes, as David says whether you get Black or Bold depends on the font. To support other replies, might be easiest to create a character style that does this for you. You can apply a keyboard shortcut to character styles. It won't be Cmd+B, but it would still make formatting one step.
Not to pile on, but it's a basic that the sooner you stop using Word/word processor methods, the sooner you will unlock the real power that InDesign offers.
You can define a character style for Black, and assign a key to apply it. But that starts with some basic mastery of styles, so... 🙂