Mr Brown is a famous doctor who has a lot of experience dealing with teenagers.
布朗先生是一位在处理青少年问题方面有丰富经验的著名医生.
(1)这是一个复合句.其中Mr Brown is a famous doctor是主句,who...teenagers是由关系代词who引导的定语从句,修饰先行词doctor.
(2)定语从句中dealing前省略了介词in.在“……方面经验丰富”,应为have a lot of experience(in)(doing) sth.
例如：
He has a lot of experience(in)teaching．他在教学方面经验丰富.
(3)deal with是固定短语,意为“处理(问题,任务等)”.例如：
He didn't know how to deal with the accident．他不知道怎样处理这起交通事故.