Not able to show entered value for a text input in a meta box

So I’ve searched for weeks and I know there are a lot of questions about this topic but I cannot figure out how to show the value that a user inputs into a text field in a custom meta box. I get the field to show up in the meta box but when I enter text and either update or publish the post, the text goes away. I think I’m close but I can’t quite figure out how to use nonce fields while saving the post. It uses object-oriented (OOP) PHP which I’m very new to so please forgive me. I’ll give all my current code below. Any help is greatly appreciated.

This creates the content for the meta box (which is where I think I’m wrong)