remove repetitive, tough coded loops conditions c#

i have category compares 2 instances same objects, generates list differences. finished looping by pivotal collections stuffing set collections list altered (this competence some-more clarity after regard formula below). works, generates an vigilant lets me know accurately total private between "old" vigilant "new" one.

my question/concern this...it unequivocally ugly, tons loops conditions. there improved proceed store/approach this, but carrying rest heavily spontaneity groups hard-coded conditions?

    open vacant diffsteps()
    {
        try
        {
            //confirm there 2 populated objects compare
            (newstep.id != guid.empty && savedstep.id != guid.empty)
            {
                //<todo> good proceed review fast objects accurately same...hash?

                //compare stepdoc collections:
                olddocs = savedstep.stepdocs;
                newdocs = newstep.stepdocs;
                collection<stepdoc> docstodelete = new collection<stepdoc>();

                foreach (stepdoc olddoc olddocs)
                {
                    bool mislay = false;
                    foreach (stepdoc newdoc newdocs)
                    {
                        (newdoc.docid == olddoc.docid)
                        {
                            mislay = true;
                        }
                    }
                    (delete)
                        docstodelete.add(olddoc);
                }

                foreach (stepdoc doc docstodelete)
                {
                    olddocs.remove(doc);
                    newdocs.remove(doc);
                }


                //same loop(s) stepusers...omitted brevity

                //this collection users delete; collection
                //of users changed.  so, collection also needs checked 
                //to permisssions (or any destiny properties) have changed.
                foreach (stepuser user userstodelete)
                {
                    //compare two
                    stepuser olduser = null;
                    stepuser newuser = null;

                    foreach(stepuser oldie oldusers)
                    {
                        (user.userid == oldie.userid)
                            olduser = oldie;
                    }

                    foreach (stepuser newie newusers)
                    {
                        (user.userid == newie.userid)
                            newuser = newie;
                    }

                    if(olduser != zero && newuser != null)
                    {
                        (olduser.role != newuser.role)
                            updatedroles.add(newuser.name, newuser.role);
                    }

                    oldusers.remove(user);
                    newusers.remove(user);
                }

            } 
        }
        catch(exception ex)
        {
            twine errormessage =
                string.format("error generating diff between step objects {0} {1}", newstep.id, savedstep.id);
            log.error(errormessage,ex);
            throw;
        }
    }

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the targeted horizon 3.5.