How to write commands for File/Json

Question

Below is the code I made but I don't know where to start. I will be grateful for the hint.

I have no idea what i should do next..

I want to make a program that will have a few commands.

1. Adding a new planet

2. Planet Removal

3. Show the List

4. Save to JSON

5. displays planet data

    public class MyDate
    {
        public int masa { get; set; }
        public int sredni { get; set; }
   
    }
   
    public class Lad
    {
        public string PlanetName { get; set; }
   
        public MyDate Szczegoly { get; set; }
    }    
    class Program
    {
        static void Main()
        {
            string choice = Console.ReadLine();
            //string choiceup = choice.ToUpper();
            switch (choice)
            {
                case "Add":
                    Add();
                    return;
                case "Save":                    
                    break;
                case "List":
                    LoadList();
                    break;
                case "Exit":
                    return;
            }
        }       
        public static void Add()
        {           
            Console.WriteLine("Podaj nazwe planety");
            string name = Console.ReadLine();
            Console.WriteLine("Podaj mase");
            int masa = Convert.ToInt16(Console.ReadLine());
            Console.WriteLine("Podaj srednice");
            int sred = Convert.ToInt16(Console.ReadLine());            
            List<Lad> _data = new List<Lad>();
            _data.Add(new Lad()
            {
                PlanetName = name,                
               Szczegoly = new MyDate
                {
                    masa = masa,
                    sredni = sred                    
                }
            });
            var json = System.Text.Json.JsonSerializer.Serialize(_data);
            Console.WriteLine(json);            
            string json2 = JsonConvert.SerializeObject(_data, Formatting.Indented);
            File.AppendAllText(@"tescikkk.json", json2);            
        }
        static List<Lad> LoadList()
        {
            string text = File.ReadAllText(@"tescikkk.json");
            if (string.IsNullOrEmpty(text))
                return new List<Lad>() { };
            return JsonConvert.DeserializeObject<Lad[]>(text).ToList();
        }
    }