Hi there, Gabarrios.
I am William and I'm here to solve a problem.
Seems like it's either your Samsung display's hardware or software problem, or your Mac Mini's software problem.
Firstly, turn off and turn on. See if that works.
Second, directly attach a wired keyboard to your display. If it connects to your Mac, then try to adjust the brightness.
Third, the brightness itself may not be mandatory. You may have to manually adjust brightness in the display's software. You might notice a few buttons on the back, side, or bottom of the screen, and there is commonly where you can adjust the speaker's sound, display brightness, or contrast.
Hope this helps!
Sincerely,
William :)