MS OFFICE PROFESSIONAL PLUS 2016 appearance

Hello, 

can someone please help in changing my whole ms outlook layout.

my laptop is new with free ms office professional plus 2016 and when I started activating it the layout appearance is modern and the latest one but after few days i just noticed that the layout become the older one.

as you can see on below image the difference of old and new appearance, i highlighted the icon to see the clear difference.

i just want to change it back for a better feeling in working with a fresh and new look designs.

Thanks!