On my bluetooth apple keyboard the delete button is lowering my screens brightness. How do i turn off that feature?

Odd. The brightness is changed with the F! & F2 keys normally. Are your other keys working normally?

There’s only two reasons I can think of would cause this: 1) hardware failure or 2) keyboard macro software that remaps keys. Assuming you have no macro software, try un-pairing and re-pairing the keyboard to your computer. If the problem persists the keyboard may be damaged.