Thanks for your help!
I changed the code to the following:
Do While Not rstID.EOF
Set xlSheet = xlBook.Sheets("Tabelle1")
Set rstGr = CurrentDb.OpenRecordset("SELECT SAP, Geris, Pauschale, SuWID, Jahr_Y, Monat_X, BT_Name, Vertragsbeginn, Vertragsende...