no Outlook 2016/365 reading pane or pinnable left Folder View with external Monitor

Hi everbody,

i have follow setup:

1*surface 7 pro+

1*docking station with monitor (and some device) or only a lenovo usb-c hdmi adapter (same problem)

my outlook works perfect if:

my surface tablet is the primary display wirh a resolution of 2736x1834

my external display with 1920x2160 (yes its a half von 4k)

my outlook shows no reading pane or i cant pin my folder view:
my external display with 1920x2160 ist PRIMARY!
my surface display wirh a resolution of 2736x1834 ist secondary or off

when i change the display resolution from the external display to 1920x108 (FHD) for testing, it works

add; when i start outlook.exe (32/64bit equal) with compatible mode with 640x480 view i have a very small Outlook Windows, but i can see all views and co. strange

thanks and regards david