Best way to shuffle array of functions - Swift

I have an array of functions (around 250) for my quiz application that provides all the information for the quiz. This includes the question, answer, explanation & after the user has submitted their answer it includes the user answer.

Before each quiz I want to shuffle all the array and select 50 questions and use them. Would I need to make a new array that holds the 50 questions and transfer the 50 randomly selected questions into that. If so, how exactly do I go about doing that.

Also what would be the best way to store the 250 question array. Do I store that in another swift file and again, if so, how would I do that efficiently.

Thanks

class QuizQuestion {

    let question: String!
    let answer: Bool!
    let explanation: String!
    var usersAnswer: Bool?
    var answerSubmitted: Bool?
    static var dog = 1

    init(question: String, answer: Bool, explanation: String) {
        self.question = question
        self.answer = answer
        self.explanation = explanation
    }
}

    let questions = [

    QuizQuestion(question: "Do I like coffee?", answer: true, explanation: "Because it's awesome!"),
    QuizQuestion(question: "Is bacon god's gift to mankind?", answer: true, explanation: "Because it's awesome!"),
    QuizQuestion(question: "Should I take a nap right now?", answer: true, explanation: "You gotta review some code!"),
]