How to make like GP

That will require some CSS.
First edit the Headline block, in Spacing set the Border Bottom width you require, then set the Colors > Border. Then in Advanced > Additional CSS Class(es) add: dotted-border.
Publish those changes.

Then add this CSS to your site.

.dotted-border {
    border-style: dotted;
}

This post here explains the various border-style properties:

https://www.w3schools.com/cssref/pr_border-style.asp