Azelab

To have header always to be visible, just remove this code from wp-content/themes/floris/assets/css/style.css

header.hide-header:not(.fixed) {
transform: translateY(-150%);
-webkit-transform: translateY(-150%);
-ms-transform: translateY(-150%);
}

or you can add 

header.hide-header:not(.fixed) {
transform: none !Important;
-webkit-transform:none !Important;
-ms-transform:none !Important;
}