I disabled my onboard graphics card via device manager.
Popped in my new GFX card and connected all wires now when
i turn on my pc i get one beep like ussual. Then a black screen?
Completely lost.

Most modern mother boards don't require disabling your integrated graphics. They disable it automatically when they sense a video card plugged in. But, even with older boards, device manager doesn't do the trick. It needs to be done via system bios.

Make sure the card is seated properly (a flashlight would help), and make sure you have a sufficient power supply and that you have the correct power connector plugged in to your card (if it requires one).