Your first boss taught you more than they meant to. Even the bad ones.

A first job teaches the subject nobody set out to teach: how adults behave when there is money and power in the room. You learn what happens when somebody is given bad news, whether the rules apply to everyone, and how a place treats people who cannot push back, none of which your boss set out to demonstrate. Bad examples instruct as efficiently as good ones. They are just less comfortable to carry.

So write down what you are learning while you are still inside it. One list of things you would copy, one of things you never will. The second is worth as much as the first.