How to make header image responsive for mobile in rara theme – Ridhi

Hi, who can help me out with this issue.
For my website (vitpeople.nl) i used the wordpress template Ridhi from Rara theme.
The whole website is responsive for mobile etc. All the images adjust automaticly to the right size except the header image, on each page it doesn’t scale, the other content does.

Please let me know if you know how to slove this. Thanks in advance.

The page I need help with: [log in to see the link]