How to remove a gap (blank space) after header image and white background?

I have been trying to figure out two issues on my pages.
First, they have a large gap (or blank space) below the header image. This eats up the space on the page.
And, the middle of the page is a white background. I’ve checked everything and cannot find anywhere where I have the white color setting. The front page is fine, but the rest of the pages have the white middle. It shows on the bottom too (after the last row).
Check it here:

Thank you for your help.

Hello there,

Please enable the “Front Page” template for your inner pages like “Client Testimonials”. It can be managed from the below path:

Dashboard > Pages > edit a page > Page Attributes > Template > select “Front Page”.