I have an old monitor which still working fine and taking interest to have two.
Is it possible this motherboard can run both? I can't find an option to enable them, only "Primary Video Adapter" which disable each other display.
Motherboard manufacturers don't offer any support for using a graphics card and the motherboard graphics at the same time. It's one or the other, your choice.
Motherboard supports:
Three graphics output options: D-Sub, DVI-D and HDMI
Supports Triple Monitor
Supports HDMI with max. resolution up to 4K x 2K (4096x2160) @ 24Hz / (3840x2160) @ 30Hz
Supports DVI-D with max. resolution up to 1920x1200 @ 60Hz
Supports D-Sub with max. resolution up to 2048x1536 @ 60Hz