I uploaded a page header background image for the site(http://karti.viria.in/photo-gallery-category/at-sivaganga/) as per image size 1920 x 450 px. But the header image is not coming full-size pc and mobile both.

find the screenshot and give me the solution for this,
https://ibb.co/DtJgxt0
https://ibb.co/QDnSkSD
https://ibb.co/qR2pCxw
https://ibb.co/cbLK68v
https://ibb.co/ZT15KHX
here clearly mentioned