The phrase translated as "the way of righteousness" is not "the way" but "a way" so Jesus is saying that John's way isn't the only way.
The word translated as "believe" here has more the sense of trusting especially trusting a person's words. The final "believe" is in the form of an infinitive, not an active verb, so with the article before it, it acts like a noun,"the trusting."
The word translated as "repent" does not mean that. It seems the biblical translators assumed that it was a typo, because it looks like the word for "repented" in Matthew 21:30, which isn't the common word translated as repent, but this word isn't either of those words. This word starts the same, but changes only a single letter, which makes it means to "take care of." Both come from the root of "to care about" but one is the feeling and the other is the action or responsibility for doing it. This verb is in a form where the subject acts on themselves, the sense is "manage yourselves."
Christ's Words in Matthew as a Guide to 40 Days of Prayer.