nevermind i fixed it, the problem was that I didn't plug the DP in the graphic's slot but in the motherboard and thanks for helping me and have a good day sir !
When i change to DP1 there is a black screen even tho everything seems to be plugged in.
Edit: When i replug the DP1 screen it says : Display cable 1 plugged in..
Yeah i have the latest filmware wich is version 1014.1. and I kinda got mistaken. I use the HDMI cable and the DP that came with the monitor, there wasn't any HDMI cable that came with the monitor so I had to find one in the house