Header and Aside menu seperation

Hi team, we want to have the aside menu not interrupting the header menu (log, links, etc).

1. We want the header should full as what can be seen if you perform the following
(1.a) navigate to https://preview.keenthemes.com/metronic8/demo1/layout-builder.html,
(1.b) click on layout
( 1.c) select either Light Header or Dark Header and click on preview.

The header occupies all the space, which is cool.

We want to have aside menu whose height or flow will not extend to the header but be more like within the content body.

Kindly guide us on how to achieve that.

thanks