Hello. So, somehow I must've messed around with the brush settings (I dont know exactly what I did!) and now when I press:

Shift + [ or
Shift + ]

My brush head does not get bigger or smaller. Also, my eraser size does not get bigger or smaller when I use those shortcuts. I know that there is no issue with other keyboard shortcuts, as I am able to press: Shift + Z to undo or delete my previous action and it works just fine. The issue occured last night while watching a youtube tutorial on "making a new brush head" in order to get a better "hair effect". The video was on YouTube and the name of the video is: "GIMP Tutorial - How to create a CUSTOM Hair Brush!" by a person named TutsByKai. I tried to follow the instructions on the video, but if you watch the short video you will notice that as he is making his tutorial, he makes alot of different changes to his methods DURING the time he is explaining, making it slightly confusing when trying to keep up. By the way, I did not get the effect that I was looking for, nor did the video help me achieve the effect he achieved in the video. Im sure he left some key steps out of the video. Anyway, ever since I messed around with the functions of the brushes, I can seem to get the keyboard function of Shift + [ or Shift + ] to function properly and make my brush heads larger or smaller. As you may know, this feature is a critical feature for a graphic artist such as myself and I am so PISSED that not only did I mess up my shortcut function for that feature, but I cant seem to figure out how to FIX IT! I tried uninstalling and reinstalling Gimp. Same exact windows and docks popped up when I did. Please, anybody in the Gimp world.... Gimp God.... anybody. PLEASE HELP!

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Background info. The settings are in the user profile in a file menurc, it is text, you can look at it and the settings are for [ bracketright (or left) and the shift-[ brace right.

Unfortunately that last one is not recognised so correct it in Edit -> Keyboard Shortcuts in the Tools section

Look for Tool's Size: Decrease (Increase) by 10 with shortcut Shift+[ (Shift+] )
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Edit them by actually entering the Shift+[ or Shift+] to give curly-brackets or whatever is there on your keyboard. see screenshots

Click on the Save button.

IT WORKED!!! THANK YOU SO MUCH, MAN!!! YOU ARE VERY MUCH APPRECIATED!!!