Oh you are not using a header element, you built the header within the content area which is not a good practice.
I would recommend:
1. You don’t need that layout element for this layout, you can remove it.
2. You can use a block element – site header to create your custom header.
2-1. Select the container block which contains the custom header, click on the 3 dots icon, click copy.
2-2. Go to appearance > elements, create a new block element, paste the block into the element’s content area.
2-3. Select site header as the element type, select entire site as location.