Program.cs

using System;
using System.Collections.Generic;

WorkWithString();

var fibonacciNumbers = new List<int> { 1, 1 };

while (fibonacciNumbers.Count < 20)
{
    var previous = fibonacciNumbers[fibonacciNumbers.Count - 1];
    var previous2 = fibonacciNumbers[fibonacciNumbers.Count - 2];

    fibonacciNumbers.Add(previous + previous2);
}
foreach (var item in fibonacciNumbers)
    Console.WriteLine(item);

void WorkWithString()
{
    var names = new List<string> { "<name>", "Ana", "Felipe" };
    foreach (var name in names)
    {
        Console.WriteLine($"Hello {name.ToUpper()}!");
    }

    Console.WriteLine();
    names.Add("Maria");
    names.Add("Bill");
    names.Remove("Ana");
    foreach (var name in names)
    {
        Console.WriteLine($"Hello {name.ToUpper()}!");
    }

    Console.WriteLine($"My name is {names[0]}");
    Console.WriteLine($"I've added {names[2]} and {names[3]} to the list");

    Console.WriteLine($"The list has {names.Count} people in it");

    var index = names.IndexOf("Felipe");

    Console.WriteLine(index == -1 
        ? $"When an item is not found, IndexOf returns {index}"
        : $"The name {names[index]} is at index {index}");

    index = names.IndexOf("Not Found");

    Console.WriteLine(index == -1 
        ? $"When an item is not found, IndexOf returns {index}"
        : $"The name {names[index]} is at index {index}");

    names.Sort();
    foreach (var name in names)
    {
        Console.WriteLine($"Hello {name.ToUpper()}!");
    }
}