how to retain different styles in different documents during merging?

I am merging multiple documents using the following code snippet.

However, it is messing around with the styling. First document has a numbered list style and the second document has a bullet list style. But when they merged, the second document's style "bulleted list" gets overridden by the numbered list from first document. How can I retain different styles for different documents being merged?

using System;
using System.IO;
using System.Linq;
using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Wordprocessing;

namespace WordMergeProject
{
    public class Program
    {
        private static void Main(string[] args)
        {
            byte[] word1 = File.ReadAllBytes(@"..\..\word1.docx");
            byte[] word2 = File.ReadAllBytes(@"..\..\word2.docx");

            byte[] result = Merge(word1, word2);

            File.WriteAllBytes(@"..\..\word3.docx", result);
        }

        private static byte[] Merge(byte[] dest, byte[] src)
        {
            string altChunkId = "AltChunkId" + DateTime.Now.Ticks.ToString();

            var memoryStreamDest = new MemoryStream();
            memoryStreamDest.Write(dest, 0, dest.Length);
            memoryStreamDest.Seek(0, SeekOrigin.Begin);
            var memoryStreamSrc = new MemoryStream(src);

            using (WordprocessingDocument doc = WordprocessingDocument.Open(memoryStreamDest, true))
            {
                MainDocumentPart mainPart = doc.MainDocumentPart;
                AlternativeFormatImportPart altPart =
                    mainPart.AddAlternativeFormatImportPart(AlternativeFormatImportPartType.WordprocessingML, altChunkId);
                altPart.FeedData(memoryStreamSrc);
                var altChunk = new AltChunk();
                altChunk.Id = altChunkId;
                              OpenXmlElement lastElem = mainPart.Document.Body.Elements<AltChunk>().LastOrDefault();
            if(lastElem == null)
            {
                lastElem = mainPart.Document.Body.Elements<Paragraph>().Last();
            }


            //Page Brake einfügen
            Paragraph pageBreakP = new Paragraph();
            Run pageBreakR = new Run();
            Break pageBreakBr = new Break() { Type = BreakValues.Page };

            pageBreakP.Append(pageBreakR);
            pageBreakR.Append(pageBreakBr);                

            return memoryStreamDest.ToArray();
        }
    }
}