The leader received two anonymous short messages about slandering me. I think the news came from a very good colleague around me. I want to solve it harmoniously. What should I do?

If the other person really treats you as a good friend, he won't show his fangs to you. Please find out whether he did it first. If so, there is no need to treat each other as friends, but on the surface, a harmonious solution is needed. A suggestion in this regard: it may be difficult to solve his complaints with kindness.