Q) John 7:8 – Jesus says I’m not going to the festival, then he goes later. Does this mean he lied?
Jesus more likely just changed his mind. The Heavenly Father part of the trinity God Head could not make mistakes, and could see the future better than we remember the past or even see the present. But Jesus was as human as you or I, with the biggest difference being that he never sinned. Not sinning does not mean he never made a mistake or changed his mind. He started as an infant, who needed to learn and grow in maturity, and get frustrated, and have needs. He did not see everything, and was probably just navigating circumstances that resulted in his changing his mind from one decision to another.
In this case, he was concerned about going to the festival because he knew he would be in danger. For some reason he did decide to go up to the festival, but he did not want to draw attention so he kept it low key. And for good reason, because by the end of the chapter, people were hunting him down.