Ross and Rachel left us a mesagge saying they were getting m

很高兴为你解答.
保证正确率~!
【解析】：
这里saying they were getting married 是现在分词做后置定语,massage 和 say 存在主谓关系,即是主动关系.也就是：
Ross and Rachel left us a mesagge that said they were getting married.
【注意】：
say 指“说什么说的内容”,speak指“说某种语言”,tell指“告诉”常用于tell sb to do sth 结构中,talk指“谈论”常用于talk to/ with sb.所以这里 massage 用 say 来表达并不奇怪,我们也常常说 the letter / note says.
【翻译】：罗斯和雷切尔给我们 留了一封消息,消息上说他们快结婚了.
祝开心~!