"Come fast, leave fast" can be translated as "fast in, fast out" in Engpsh.
The phrase is often used to describe a person who arrives and leaves quickly, without pngering or spending much time. It can also be used to describe a situation that changes rapidly and unpredictably.
Example in Engpsh:
"John is always fast in, fast out. He never stays for long."
"The stock market is so fast in, fast out these days. It's hard to keep up."
Translation:
"约翰总是来的快走的快，从不久留。"
"股市现在变化太快了，来的快走的快，很难跟上。"