Yes, if you genuinely believe something that is not true and you convey that information to others, it is still considered a lie. A lie is defined as a false statement made with the intention to deceive. Intent is a crucial aspect of lying. Even if you sincerely believe something that turns out to be false and share it as if it were true, the information you present is still misleading to others, which constitutes a lie.
It's essential to be mindful of the accuracy of the information we share with others and to verify facts before conveying them to avoid unintentionally spreading misinformation. If you discover that something you believed to be true was, in fact, false, it is essential to correct the misconception and clarify the truth with those who were exposed to the incorrect information.