cage.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Rabbits
{
    public class Cage
    {
        private List<Rabbit> data;

        public Cage(string name, int capacity)
        {
            this.Name = name;
            this.Capacity = capacity;
            this.data = new List<Rabbit>();
        }
        public string Name { get; private set; }
        public int Capacity { get; private set; }
        public int Count => this.data.Count();//getter Count

        //adds an entity to the data if ima mqsto//////
        public void Add(Rabbit rabbit)
        {
            if (this.data.Count < this.Capacity)
            {
                data.Add(rabbit);
            }

        }
        //removes a rabbit by given name, if such exists, and returns bool///
        public bool RemoveRabbit(string name)
        {
            return this.data.Remove(this.data.FirstOrDefault(x => x.Name == name));
        }
        //removes all rabbits by given species//
        public void RemoveSpecies(string species)
        {
            this.data.RemoveAll(x => x.Species == species);
        }
        //sell (set its Available property to false without removing it from the collection) the first rabbit with the given name, also return the rabbit///
        public Rabbit SellRabbit(string name)//pyrviq zaek s dadeno ime
        {
            Rabbit sell = this.data.FirstOrDefault(x => x.Name == name);
            sell.Available = false;
            return sell;
        }
        //sells (set their Available property to false without removing them from the collection) and returns all rabbits from that species as an array///
        public Rabbit[] SellRabbitsBySpecies(string species)
        {
            List<Rabbit> rabbits = new List<Rabbit>();
            rabbits = this.data.Where(x => x.Species == species).ToList();
            for (int i = 0; i < rabbits.Count; i++)
            {
                rabbits[i].Available = false;
            }
            return rabbits.ToArray();
        }
        ///returns a string in the following format, including only not sold rabbits//vkl samo neprodadeni zaici
        public string Report()
        {
            StringBuilder sb = new StringBuilder();

            sb.AppendLine($"Rabbits available at {this.Name}:");

            foreach (var rab in this.data)
            {
                if (rab.Available == true)
                {
                    sb.AppendLine($"{rab}");
                }
            }
            return sb.ToString().TrimEnd();
        }

    }
}
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rabbit.cs:
using System;
using System.Collections.Generic;
using System.Text;

namespace Rabbits
{
    public class Rabbit
    {
        public Rabbit(string name, string species)
        {
            this.Name = name;
            this.Species = species;
            this.Available = true;
        }

        public string Name { get; private set; }
        public string Species { get; private set; }
        public bool Available { get; set; }

        public override string ToString()
        {
            return $"Rabbit ({ this.Species}): {this.Name}";
        }
    }
}
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startUp.cs:
namespace Rabbits
{
    using System;
    using System.Linq;

    public class StartUp
    {
        public static void Main()
        {
            //Initialize the repository (Cage)
            Cage cage = new Cage("Wildness", 20);
            //Initialize entity
            Rabbit rabbit = new Rabbit("Fluffy", "Blanc de Hotot");
            //Print Rabbit
            Console.WriteLine(rabbit); //Rabbit (Blanc de Hotot): Fluffy

            //Add Rabbit
            cage.Add(rabbit);
            Console.WriteLine(cage.Count); //1
                                           //Remove Rabbit
            cage.RemoveRabbit("Rabbit Name"); //false

            Rabbit secondRabbit = new Rabbit("Bunny", "Brazilian");
            Rabbit thirdRabbit = new Rabbit("Jumpy", "Cashmere Lop");
            Rabbit fourthRabbit = new Rabbit("Puffy", "Cashmere Lop");
            Rabbit fifthRabbit = new Rabbit("Marlin", "Brazilian");

            //Add Rabbits
            cage.Add(secondRabbit);
            cage.Add(thirdRabbit);
            cage.Add(fourthRabbit);
            cage.Add(fifthRabbit);

            //Sell Rabbit by name
            Console.WriteLine(cage.SellRabbit("Bunny")); //Rabbit (Brazilian): Bunny
                                                         //Sell Rabbit by species
            Rabbit[] soldSpecies = cage.SellRabbitsBySpecies("Cashmere Lop");
            Console.WriteLine(string.Join(", ", soldSpecies.Select(f => f.Name))); //Jumpy, Puffy

            Console.WriteLine(cage.Report());
            //Rabbits available at Wildness:
            //Rabbit (Blanc de Hotot): Fluffy
            //Rabbit (Brazilian): Marlin
        }
    }
}