Proficient是指工作和任务非常熟练高效,Proficient is the ability to do a job or task in an efficient manor correctly.
"People think I am a proficient typist, but that is only because I am fast. I make mistakes quite often."
fluent是指语言和动作非常轻松,Fluent is having enough skill/knowledge of movement/language that it is almost effortless.
"Her ballet is wonderful! Every move she makes is so fluent.". Or "Your English is so fluent that I thought you grew up speaking it."