Yes, it is possible for a person to speak five languages fluently. This would depend on where a person lived, his exposure to multiple languages, and ability to use the languages to satisfy social needs. Let me give you some examples. There are a number of people in Taiwan who are fluent from childhood in four languages, and if they go abroad for study in Japan, they will have fluency in five languages. If a person is born into a Hakka family, the first language they will hear is Hakka. Before the age of five, they will have playmates whose native language is Taiwanese. After they start formal school at the age of six, they will start learning Chinese Mandarin and English. Finally, if they want to do study in Japan, they will start learning Japanese in high school and become proficient in it through immersion in Japan. The same situation would apply to people who are brought up in Switzerland where Italian, German, French, and English are spoken from childhood. If another language is elected in school, a person can become fluent in five languages!