Editing the Burger Menu

How do I modify the “burger” menu? Right now it’s too thick and I want to make the stripes thinner

Here is my site Read-Only: LINK
(how to share your site Read-Only link)

You can’t natively make the stripes thinner but you can manually add another icon into the blog instead of the existing one. If your background is solid, you can also add text shadows to the icon in the same color as the background in a solid way so that it will fake making it thinner.