C# iTextSharp to manipulate tagged pdf structure

Question

I want to manipulate (modify) a fully tagged pdf. Using below code i am able to get the document tree structure

PdfDictionary catalog = reader.Catalog;
PdfDictionary struc = catalog.GetAsDict(PdfName.STRUCTTREEROOT);

now I want to modify the below structure

Incorrect tagging structure

want to remove tag which is inside the tag, and also move the content from to

to

Correct tagging structure

Please guide me, I have little bit knowledge of coding.