Ok I have found the issue and it's not a bad new !
The monitor is native 3840x1080
https://imgur.com/a/KPxnwLlIf I have remove DSC and activate DLDSR x1.78, it's 5120x1440 !!! And it's blurry !!
SO WE CANT HAVE DLDSR WITH THIS MONITOR FOR THE NEW BUY...