Slang is the language you speak with your friends and usually it is not the thing you learn from your teachers. Not every slang has an exact Chinese counterpart, some some do or close to a Chinese slang.
“Bummer” is used to express one’s sadness and disappointment when something is happened accidentally and unexpectedly. Something is not right and it is a “bummer”. In Chinese, it could be “倒霉”.
“What a bummer!” is “太倒霉了” or “真倒霉”。
“I dropped my phone in the toilet. Bummer.” “我的电话掉进马桶了。倒霉！“
你今天有倒霉的事儿发生吗？
