So i played OW last on june 11 it was working fine at that time. But now when i am trying to launch the game only a black screen opens open nothing happens 
can anyone please help me how to fix it?
Do you have Razer brand devices? If so, then this sounds like the Razer Chroma SDK issue. If you have Razer Synapse on your system, try updating to Razer Synapse 3 - Cloud-Based Hardware Configuration Tool | Razer United States. This should update the Razer Chroma SDK and prevent the crashes on launch.
OK guys found the solution. For anyone having same problem as me i am using gtx 1080 and the problem was the latest nvidia drivers i just rolled back previous version and game started to work fine.