how to make header sticky

[swawestore]

I want to make my header sticky and decrease its height on my site https://swawe.store/
demo site link https://bluorng.com/

[BSSCommerce-TA]

@swawestore, add this css code below at the bottom of "base.css" or "theme.css" file: 

div#shopify-section-sections--15945048817754__announcement-bar {
    position: sticky;
    top: 0px;
    z-index: 1000;
}
.shopify-section.shopify-section-group-header-group.section-header {
    top: 25px !important;
}

If it works please choose my answer as solution. Thank you.