How to update existing record of list one of two in Event Receiver

Question

I have got a problem how to update Secound list which is made by First list. All must be in Event Receiver. How Can I made difrent Event Receivers update to Diferent Lists Could You Help me with his. I have got a Adding items which look like like this:

   public override void ItemAdding(SPItemEventProperties properties)
   {
       base.ItemAdding(properties);

       if (properties.List.Title == "Wpisy")
       {
           SPSite oSiteCollection = new SPSite("http://wasp03/");
           SPWeb witryna = oSiteCollection.RootWeb;
           SPListItemCollection listaDniSwiatecznych = witryna.Lists["DR2013 Święta"].Items;
           SPListItemCollection listaDniUrlopowych = witryna.Lists["ListaUrlopow2012"].Items;
           SPList lstOtherList = properties.Web.Lists["Szczegoly"];
          // lstOtherList.EnableThrottling = false;

           // Makking two veriables One the day start, and one the day stop
           dzienStart = new DateTime();
           dzienStop = new DateTime();
           // setting two fields from propeties
           dzienStart = Convert.ToDateTime(properties.AfterProperties["DzienStart"]).ToUniversalTime();

           dzienStop = Convert.ToDateTime(properties.AfterProperties["DzienStop"]).ToUniversalTime();

           // Setting a loop while which should be done until the propeties from dzienstart don't equal with dzienstop


           while (dzienStart <= dzienStop)
           {

               if (!RozliczSwieta(oSiteCollection, witryna, listaDniSwiatecznych))
               {
                   continue;
               }
               if(!RozliczUrlopy(oSiteCollection, witryna, listaDniUrlopowych, properties))
               {
                   continue;
               }

                // If are check out that the date are in weekends or not
                       if (dzienStart.DayOfWeek.ToString() == "Saturday" || dzienStart.DayOfWeek.ToString() == "Sunday")
                       {
                           // If a veriable equal Saturday, or sunday they day increase by one 
                           dzienStart = dzienStart.AddDays(1.0);
                           continue;
                       }
                       // In the others hand the object is adding on the list 
                       else
                       {
                           SPListItem item = lstOtherList.Items.Add();
                           item["Kontrakt"] = properties.AfterProperties["Kontrakt1"];
                           item["Pracownik"] = properties.UserDisplayName;
                           item["Dzien"] = dzienStart;
                           item["Procent"] = properties.AfterProperties["Procent"];
                           SPFieldLookup lookup = (SPFieldLookup)properties.List.Fields["Procent"];
                           Int32 singlelookupItemID = Convert.ToInt32(properties.AfterProperties["Procent"]);
                           string lookupval = properties.Web.Lists[new Guid(lookup.LookupList)].GetItemById(singlelookupItemID)[lookup.LookupField].ToString();
                           item["Procent_wartosc"] = lookupval;
                           SPList listaWpisy = properties.Web.Lists["Wpisy"];
                           SPListItemCollection listaKontrakty = listaWpisy.Items;
                           foreach (SPListItem kontrakt in listaKontrakty)
                           {
                               item["ID Czas Pracy Wpisy"] = new SPFieldLookupValue(kontrakt.ID, kontrakt.ID.ToString());
                               item["ID_z_Wpisy"] = kontrakt.ID+1;
                           }
                           dzienStart = dzienStart.AddDays(1.0);

                           item.Update();
                       }


           }

       //    SPUtility.Redirect("http://gzawistowskilap/SitePages/Close.aspx?IsDlg=1", SPRedirectFlags.Default, current);

       }



   }

What should I vrite to items update to update some sort of items ?

Edited about Wood answer:

So i should do like this:

SPListItem originalItem = //Get the item with the method you need from the original list most likely from enumerating the original list?
SPListItem item = list.Items.Add();

item["field1"] = originalItem["field1"];
item["field2"] = originalItem["field2"];
item["field3"] = originalItem["field3"];
item["field4"] = originalItem["field4"];
item.Update()

[Edited to take into account your changes, correcting the code]

Answer 1

At a glance that code should work all you need to do is a little modification and maybe clean it up so it's easier for you to follow, it gets a little crazy but the basics of adding an item are:

SPListItem originalItem = //Get the item with the method you need from the original list most likely from enumerating the original list?
SPListItem item = list.Items.Add();
item["field"] = originalItem["field"];
item.Update()

With that in mind, you can copy the fields over from one items to the new item and update it. I would do it one field at a time, doing the whole item won't work as you intend.