Strings Mix Complete, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string s1 = "A generation must confront the looming";
            string s2 = "codewarrs";
            Console.WriteLine("1:nnnnn/1:ooooo/1:tttt/1:eee/1:gg/1:ii/1:mm/=:rr");
            Console.WriteLine();
            string s3 = StringsMix("Lords of the Fallen", "gamekult");
            Console.WriteLine(s3);
        }
	
        public static string StringsMix(string s1, string s2)
        {
            bool s1Contain = s1.GroupBy(x => x).Any(g => g.Count() > 1);
            bool s2Contain = s2.GroupBy(x => x).Any(g => g.Count() > 1);
            
            if (s1Contain || s2Contain)
            {
                StringBuilder sb = new StringBuilder();
                char[] s1Chars = s1.Where(x => char.IsLower(x)).OrderBy(x => x).ToArray();
                char[] s2Chars = s2.Where(x => char.IsLower(x)).OrderBy(x => x).ToArray();
                
                for (int i = 97; i < 122; i++){
                    char[] s1Ch = s1.Where(x => x.Equals((char)i)).ToArray();
                    char[] s2Ch = s2.Where(x => x.Equals((char)i)).ToArray();
                    int s1Count = s1Ch.Length;
                    int s2Count = s2Ch.Length;
                    
                    if (s1Count > s2Count)
                    {
                        string chars = new String(s1Ch);
                        sb.Append("1:" + chars + "/");
                    }
                    else if (s2Count > s1Count)
                    {
                        string chars = new String(s2Ch);
                        sb.Append("2:" + chars + "/");
                    }
                    else if (s1Count == s2Count)
                    {
                        string chars = new String(s1Ch);
                        sb.Append("=:" + chars + "/");
                    }
                }
                if (sb.ToString().Length <= 1) return "";
                string final = String.Empty;
                var specialOrder = "12=";
                string[] strings = sb.ToString().Split('/');
                
                final = String.Join("/", strings);
                strings = final.Split('/').Where(x => x.Length > 3).Select(x => x).ToArray();
                final = String.Join("/", strings);
                strings = final.Split('/').OrderByDescending(x => x.Length)
                                          .ThenBy(s => specialOrder.IndexOf(s[0]))
                                          .ThenBy(s => s).ToArray();
                final = String.Join("/", strings);
                return final;   
            }
            return "";
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,17 sec, absolute running time: 0,13 sec, cpu time: 0,11 sec, average memory usage: 18 Mb, average nr of threads: 4