Hi Emzi,
This is standard behavior with WordPress, I’m afraid.
You can set a more standard navigation in Customize > Posts > Single Post > Layout. As this is not breaking the page, hiding this is considered customization work. Unfortunately, this is a service that we do not provide. We only share snippet only to solve issues with our theme. Any further request for CSS snippets will have to be part of a defect that needs to be fixed urgently. No snippets will be shared otherwise.
If you want to go further with the customization of your website, we advise that you hire a freelancer to do it for you.
If you’re on a tight budget, we recommend you to require the services from Fiverr. This web platform gives you access to developers who already have experience with theme customizations, and for very competitive prices.
Disclaimer : we have no affiliation with Fiverr and are only recommending it as a starting point and a popular option for those who might not be sure where to look when in need of some custom work.
Thank you for your understanding.