Hello,
1) It’s because of the size of your images. Even if you use the negative margin it keeps its height and the header block takes it. I have made some changes to reduce it. Check, please.
2) Add the below code to custom CSS to fix the images in the sticky header
.sticky-on .rat-logo {
max-width: 120px;
margin-top: 0 !important;
}
.sticky-on .main-logo {
max-width: 80px;
margin-top: 0 !important;
}
Regards