[ubuntu] Hyper-V Resolution - Windows 10

Hello,
I tried to install ubuntu on my Hyper-V VM (windows 10 pro) but it showed only in a small window.
I read in some posts that "grub" needs to changed so I tried these settings :

http://i.imgsafe.org/0e65f91eae.png

http://i.imgsafe.org/0e66184b67.png

My resolution is 4K but when I set it in these settings.. It changes to lower resolution so I tried FHD.
This is the result :

http://i.imgsafe.org/0e7832bb0b.png

I've tried to view full screen but it's the same (expect black background).

BTY : Is the Hyper-V suppose to be so slow?
I have 32gb ram and i7 skylake CPU..
Thanks for any help,
Roy.