>> What can i do to fix this matter??? Did i do anything wrong?
There may be an auxiliary power supply plug you have missed. Just check in case you have missed this.
Standard test is to remove motherboard from case and place on a piece of cardboard and connect power supply wires to it and then try rebooting. Removal from case takes care of the chance there is a bad earth occurring.
Disconnect all drives while on cardboard and any extra cards. Just leave the graphics card and one stick of memory. Try booting like this.