When you have a complex problem, it's helpful to talk it through with someone objective.

talk 是动词，意思是"交谈、讨论"。 it 是代词，指代前文提到的"复杂问题"。 through 在这里是副词，表示"彻底地、完整地"。 talk it through 是一个固定短语，意思是"彻底讨论、详细分析"，指通过充分交谈来理清问题的各个方面。