how can I change this:
To this:
The site you try to copy (swapd), I assume they use the stable version of Discourse or an older beta version. That’s why they still have the older ux. The second top menu image what you shared was changed in Discourse to the more modern first top menu image you shared. So you can’t change it back.
My opinion: Don’t insist on everything looking the same, because by the time you’re done, you can start over with everything because the site you copied will also be updated and your site will be outdated. I’ve already noticed this in your previous topics, but it’s not that simple. If I remember correctly, the owner of swapd said in the past that they spent thousands of dollars on the development of various unique components and plugins.
Be unique. People will much love the more modern design…