An Einspruch must be in writing or via ELSTER and should say which notice you object to. Reasons can follow later, but the deadline cannot be extended.
Filing an objection does not stop the payment obligation automatically. For that, you need a separate application for suspension (Aussetzung der Vollziehung).
Full guideReceived a letter from the German tax office? What to do nowRelated terms
General information on German tax law, not advice on your individual case.