WoodMart theme has top and bottom paddings for Main page wrapper in order to ensure WooСommerce templates nice view.
However, this padding causes the gap between header and main content on home page of some of the demo pages. In order to get rid of it enter the page: Dashboard > pages > find the page > edit and set margin-top:-40px in the upper row settings:
Dark color of footer and pre-footer backgrounds make the Main page wrapper bottom padding visible and a white space between the pre-footer and footer occurs:
In order to remove the gap, enter the HTML block, which is used in the Theme Settings > Footer > Pre-footer area and set margin-bottom: - 40px; to the row. If there are a few rows in the template, the margin should be set to the last one.
If there is not pre-footer, however the last row of the continent has the color or image background the gap may occur between the content and the footer. In this case you should set margin-bottom for the last row in the page. Here is the example of the gap https://woodmart.xtemos.com/demo-drinks/demo/drinks/