This is why you'll want to read those primary sources as part of a class, instead of just trying to go it alone.
But even that won't save you from "bad readings" of Nietzsche or any other philosopher, as plenty of experts disagree on what he meant. He, like some other philosophers, just wrote in a way that doesn't have one obvious meaning that everyone can agree on. With experience and study, you can make up your own mind, which will be better than swallowing some other person's pre-digested interpretation of him.
You might have an easier time understanding a secondary source's interpretation of Nietzsche, but that doesn't mean that you understand Nietzsche.