import java.util.Scanner;
 public class ProgrammKonsole {
     public static void main(String[] args) {
         int n;
         String patientname;
         String patientvorname;
         String geschlecht;
         String krankenkasse;
         int alter;
         int fallzahl = 0;

         Scanner sc = new Scanner(System.in);
         n = sc.nextInt();

         while (n < 5) {
             System.out.println("Willkomme in dem Patientmanagement-tool");
             System.out.println("Wahlen Sie zwischen 1- 5");
             System.out.println("1 - Um einem neuen Patient anzulegen");
             System.out.println("2 - Um dem letzen eingegebenen Daten anzuzeigen");
             System.out.println("3- Um dem Fallzahl anzuzeigen");
             System.out.println("4- Um allen Vorhandene Info anzuzeigen");
             System.out.println("5- Um das Programm zu beenden");


             n = sc.nextInt();

             switch (n) {
                 case 1:
                     System.out.println("Neuen Patient anlegen");


                     System.out.println("Wurde den Patient in den letzten 24 Stunden schon für den selben Fall behandelt?");
                     String patient = sc.nextLine();

                     if (patient.equals("nein")) {
                         fallzahl = fallzahl++;
                         System.out.println("Fallzahl: " + fallzahl);
                     }


                     System.out.println("Name:");
                     patientname = sc.next();


                     System.out.println("Vorname:");
                     patientvorname = sc.next();

                     System.out.println("Geschlecht:");
                     geschlecht = sc.next();

                     System.out.println("Alter:");
                     alter = sc.nextInt();

                     System.out.println("Krankenkasse:");
                     krankenkasse = sc.next();
                     break;


                 case 2:
                     System.out.println("Letzte eingegebene Daten anzeigen");

                     System.out.println("name:" + patientname);
                     System.out.println("vorname" + patientvorname);
                     System.out.println("Geschlecht" + geschlecht);
                     System.out.println("Alter" + alter);
                     System.out.println("Krankenkasse" + krankenkasse);
                     break;


                 case 3:
                     System.out.println("Fallzahl anzuzeigen");
                     System.out.println("Fallzahl" + fallzahl);
                     break;


                 case 4:
                     System.out.println("Alle Info Anzeigen");
                     System.out.println("name:" + patientname);
                     System.out.println("vorname" + patientvorname);
                     System.out.println("Geschlecht" + geschlecht);
                     System.out.println("Alter" + alter);
                     System.out.print("Krankenkasse" + krankenkasse);
                     System.out.println("Fallzahl" + fallzahl);
                     break;


                 case 5:
 
 
                      System.out.println("Das Programm beenden");
                       break;
             }

         }
     }
 }

i was trying to build a console application for a school project, i ve found this described error in after the case number 2´, where it said , that all the string variables and int variable “Alter” aren t declared.
i ve already tried to change the position of the strings, or doing something else, but i come back everytime to this kind of error, that as well is repeated for the case 4, only the variable Fallzahl gives no kind of problems