the dvi port on the RX series of graphics cards is a DVI-D type meaning a digital only signal. VGA is an analogue signal. So you need an active digital to analogue adaptor. They normally come with a socket for mini usb cable to power it. This is the same for display port so be on your guard for cheap unpowered adaptors that do not work. . Here's a link explaining in more detail http://www.pcadvisor.co.uk/how-to/pc-peripheral/how-tell-dvi-i-dvi-d-cables-apart-3365585/ Your second photo, lots of people have bought this adaptor only to find out they do not work.
just looked at specs on your monitor it says dvi-d and vga connector. if it has dvi-d just buy a dvi-d to dvi-d cable
When using the Display port Adaptor I had to add 1080p display setting using the Radeon Additional Settings HDTV support. tick 1080p 50Hz or 60Hz.
further down the page select 1080p 50Hz or 60Hz
then apply format
for some strange reason the windows screen size adapter set it self to 59 Hz and screen wasn't centralised. I changed windows screen size adaptor to 60Hz and it centralised