Brigtness (clouds) and HDR switching On and Off

I have a new Monitor, a curved MSI Optix MAG322CQR
And i struggle to find settings where the clouds are not to bright. GPU is a 1070
Also i have a second problem. If i turn HDR on, Windows / and Game, every time i switch to the second Monitor, the screen on the MSI goes shortly black. I guess in the moment the other Window is in focus.
Geforce Driver is 466.27