I translate the sentence into Chinese : I have already missed the mountain in Shanghai , how could I miss the sea again in shanghai ? This means : I have already missed something wonderful so I won't miss some other good things again! I hope it can help you^_^

這是 反問 (反詰) 修辭 用疑問的形式來表示確定的意思，叫反問。 通常是否定句表達肯定意，肯定句表達否定意。 反問的作用是加強語氣，把意思表達得更強烈。 例：孔子能夠成為百代景仰的聖人，難道真是天生成的？ "错过了上海的一座山，怎能再错过上海的一片海？" 即 "你不能錯過上海所有的山景和海景"

Having missed a mountain of Shanghai,how can I miss the sea of Shanghai?

What the sentence lets us konw that we should learn to cherish what you have

Actually Advertisements always exaggerate, It is same with a Chinese saying "过了这村就没这店" which means you have to grasp the last chance ASAP.