Answers for "how fixed div in header on scroll"

fixed div with scrollable content

.fixed-content {
    overflow-y:scroll;
    overflow-x:scroll;
}

css static header on scroll

table thead,
table tfoot {
  position: sticky;
}
table thead {
  inset-block-start: 0; /* "top" */
}
table tfoot {
  inset-block-end: 0; /* "bottom" */
}