static void Main(string[] args) { //Some parametres for window Console.WindowHeight = 50; Console.WindowWidth = 120; Console.Title = "Awesome Calculator"; //### string answer = ""; Console.WriteLine("What do You want to calculate?\n"); Lists("Main menu"); answer = Console.ReadLine(); while (answer != "Exit" || answer != "exit") // Main loop for main menu { if (answer == "Solids" || answer == "solids" || answer == "1") // Checking if answer is for solids... { while (answer != "Back") { Console.Clear(); Solids.SolidsFunc(); Solids.Exit(ref answer); } } else if (answer == "Flat geometry" || answer == "Flat Geometry" || answer == "flat Geometry" || answer == "2") // ... or flat geometry { while (answer != "Back") // Loop for flat geometry with switch. Breaking if You'll type "back". { Console.Clear(); Console.WriteLine("What do You want to calculate? (Flat geometry)\n"); Lists("Flat geometry"); answer = Console.ReadLine(); //Switch that checks which shape you want to calculate switch (answer) { case "Square": case "1": { FlatGeometry.Square(); break; } case "Triangle": case "2": { FlatGeometry.Triangle(); break; } case "Rectangle": case "3": { FlatGeometry.Rectangle(); break; } case "Parallelogram": case "4": { FlatGeometry.Parallelogram(); break; } case "Diamond": case "5": { FlatGeometry.Diamond(); break; } case "Trapeze": case "6": { FlatGeometry.Trapeze(); break; } case "Circle": case "7": { FlatGeometry.Circle(); break; } case "Deltoid": case "8": { FlatGeometry.Deltoid(); break; } default: break; } } } else if (answer == "Back" || answer == "back") //If statement that makes you can go back { Console.Clear(); Console.WriteLine("You are now here: Main menu\n"); Lists("Main menu"); answer = Console.ReadLine(); } else { Console.Clear(); Console.WriteLine("I'm sorry, can You repeat? You are here: Main menu\n"); Lists("Main menu"); answer = Console.ReadLine(); } } }