Hi Jonas,
I'm checking your store, but as I can see, the product page shows up fine for me. Let me know what is exactly the exact issue is with the product gallery.

Please note that on smaller desktops, we automatically resize the product photo so that the thumbs can show up. If that is your issue, that is done on purpose; otherwise, the image will be just cropped on the bottom.
Regarding the header request, we can help you do that. If that's ok for you, let me know your store's 4-digit collaborator code, and we will send a partner request, but my suggestion is to keep it as it is, as the header is revealed on scroll up, so the spacing is not an issue.