C#-Code

 static void Main(string[] args)
        {
            Console.WriteLine($"Lösung: {Check(Wort: "mama", Kiste: "mneamna")}");
            Console.WriteLine($"Lösung: {Check(Wort: "papa", Kiste: "aapq")}");
            Console.WriteLine($"Lösung: {Check(Wort: "aabaacbaacbb", Kiste: "bbaabaaccaaa")}");

            Console.ReadLine();
        }

        static bool Check(string Wort, string Kiste)
        {
            CharValueCollection wortCollection = new CharValueCollection();
            CharValueCollection kisteCollection = new CharValueCollection();
            int counter = 0;

            for (int i = 0; i < Wort.Length; i++)
            {
                counter = 0;
                if (!wortCollection.containsChar(Wort[i].ToString()))
                {
                    for (int j = 0; j < Wort.Length; j++)
                    {
                        if (Wort[i] == Wort[j])
                            counter++;
                    }
                    wortCollection.addCharValue(new CharValue(Wort[i].ToString(), counter));
                }
            }

            for (int i = 0; i < Kiste.Length; i++)
            {
                counter = 0;
                if (!kisteCollection.containsChar(Kiste[i].ToString()))
                {
                    for (int j = 0; j < Kiste.Length; j++)
                    {
                        if (Kiste[i] == Kiste[j])
                            counter++;
                    }
                    kisteCollection.addCharValue(new CharValue(Kiste[i].ToString(), counter));
                }
            }

            foreach (CharValue charValueWort in wortCollection.charValues)
            {
                foreach (CharValue charValueKiste in kisteCollection.charValues)
                {
                    if ((charValueKiste.Value == charValueWort.Value) &&
                        !(charValueKiste.Count >= charValueWort.Count))
                        return false;
                }
            }
            return true;
        }

        class CharValueCollection
        {
            public List<CharValue> charValues { get; set; }

            public CharValueCollection()
            {
                charValues = new List<CharValue>();
            }

            public void addCharValue(CharValue value)
            {
                this.charValues.Add(value);
            }

            public bool containsChar(string value)
            {
                return charValues.Count <= 0 ? false : charValues.Where(x => x.Value == value).Count() > 0;
            }
        }

        class CharValue
        {
            public string Value { get; set; }
            public int Count { get; set; }

            public CharValue(string Value, int Count)
            {
                this.Value = Value;
                this.Count = Count;
            }
        }

C#-Code

using System;
using System.Collections.Generic;

var l = new List<(string word, string box)> { ("mama", "mneamna"), ("papa", "aapq"), ("aabaacbaacbb", "bbaabaaccaaa") };
l.ForEach(x => Console.WriteLine(IsConstructible(x.word, x.box)));

static bool IsConstructible(string word, string box)
{
    var c = new int[26];
    if (word == box) return true;

    for (int i = 0; i < box.Length; i++)
        c[box[i] - 'a']++;

    for (int i = 0; i < word.Length; i++)
        if (c[word[i] - 'a']-- <= 0)
            return false;

    return true;
}