Hello,
Yes, you can remove the header image, though the CSS code by selecting page ID. In terms of making smaller height, please copy below CSS code and follow the simple steps;
body .wrap-inner-banner .page-header {
margin-bottom: 10%;
margin-top: 20%;
}
Note: The values of % are default values. Please do change it as per your requirement.
Then, Go to Dashboard > Appearance > Customize > Additional CSS and paste and click on the publish button. That’s it.
Thanks.