One is still telling the truth and the other is telling a lie. What's the use of telling the truth and sometimes telling lies?

The first monk sometimes tells the truth and sometimes lies, the second monk tells lies and the third monk tells the truth. According to relevant information, the first monk answered the truth, that is, the second monk told the truth, but the second monk said that he sometimes told the truth and sometimes lied, which led to contradictions. The first monk didn't tell the truth, that is, the second monk is not a monk who tells the truth, and he won't be a monk who tells the truth, so the third monk tells the truth, that is, the second monk tells the truth.