Untitled

int selectedIndex = 0;

string[] menu = new string[]
{
    "Book",
    "Settings",
    "Exit"
};

while (true)
{
    Console.Clear();

    Console.WriteLine("Menu");

    for (int i = 0; i < menu.GetLength(0); i++)
    {
        if (selectedIndex == i)
        {
            Console.ForegroundColor = ConsoleColor.Blue;
            Console.WriteLine($"{i + 1}. {menu[i]} <<<");
        }
        else
        {
            Console.ResetColor();
            Console.WriteLine($"{i + 1}. {menu[i]}");
        }
    }

    ConsoleKeyInfo keyInfo = Console.ReadKey();

    switch (keyInfo.Key)
    {
        case ConsoleKey.UpArrow:
            if (selectedIndex > 0)
            {
                selectedIndex--;
            }
            break;

        case ConsoleKey.DownArrow:
            if (selectedIndex < menu.GetLength(0) - 1)
            {
                selectedIndex++;
            }
            break;

        case ConsoleKey.Enter:
            if (selectedIndex == 0)
            {
                Console.Clear();

                ShowSeats();

                Console.ReadKey();
            }
            else if (selectedIndex == 1)
            {
                Console.Clear();
                Console.WriteLine("Here are some settings");
                Console.ReadKey();
            }
            else if (selectedIndex == 2)
            {
                Console.Clear();
                Console.ResetColor(); 
                return;
            }
            break;
    }

    Console.ResetColor();

}

static void ShowSeats()
{

    int selectedIndexY = 0;
    int selectedIndexX = 0;
    while (true)
    {   Console.Clear();
        string[,] aviaTickets = new string[6, 4]
        {
    { " [A1] ", " [A2] "," [A3] "," [A4] " },
    { " [B1] ", " [B2] "," [B3] "," [B4] " },
    { " [C1] ", " [C2] "," [C3] "," [C4] " },
    { " [D1] ", " [D2] "," [D3] "," [D4] " },
    { " [E1] ", " [E2] "," [E3] "," [E4] " },
    { " [F1] ", " [F2] "," [F3] "," [F4] " }
        };

        Console.WriteLine("Book");

        for (int i = 0; i < aviaTickets.GetLength(0); i++)
        {
            for (int j = 0; j < aviaTickets.GetLength(1); j++)
            {
                if (i == selectedIndexY && j == selectedIndexX)
                {
                    Console.ForegroundColor = ConsoleColor.Green;
                }
                else
                {
                    Console.ResetColor();
                }

                Console.Write(aviaTickets[i, j]);
            }
            Console.WriteLine();
        }

        ConsoleKeyInfo keyInfo = Console.ReadKey();
        switch (keyInfo.Key)
        {
            case ConsoleKey.UpArrow:
                {
                    if (selectedIndexY > 0)
                    {
                        selectedIndexY--;
                    }
                }
                break;
            case ConsoleKey.DownArrow:
                {
                    if (selectedIndexY < aviaTickets.GetLength(0) - 1)
                    {
                        selectedIndexY++;
                    }
                }
                break;

            case ConsoleKey.LeftArrow:
                {
                    if (selectedIndexX > 0)
                    {
                        selectedIndexX--;
                    }
                }
                break;
            case ConsoleKey.RightArrow:
                {
                    if (selectedIndexX < aviaTickets.GetLength(1) - 1)
                    {
                        selectedIndexX++;
                    }
                }
                break;
        }
        Console.ResetColor (); 
    }
}