diff --git a/src/main/java/EST/MiJo/Main.java b/src/main/java/EST/MiJo/Main.java
index ba6142a..72ded1f 100644
--- a/src/main/java/EST/MiJo/Main.java
+++ b/src/main/java/EST/MiJo/Main.java
@@ -1,17 +1,142 @@
 package EST.MiJo;
 
-//TIP To <b>Run</b> code, press <shortcut actionId="Run"/> or
-// click the <icon src="AllIcons.Actions.Execute"/> icon in the gutter.
-public class Main {
-    public static void main(String[] args) {
-        //TIP Press <shortcut actionId="ShowIntentionActions"/> with your caret at the highlighted text
-        // to see how IntelliJ IDEA suggests fixing it.
-        System.out.print("Hello and welcome!");
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
 
-        for (int i = 1; i <= 5; i++) {
-            //TIP Press <shortcut actionId="Debug"/> to start debugging your code. We have set one <icon src="AllIcons.Debugger.Db_set_breakpoint"/> breakpoint
-            // for you, but you can always add more by pressing <shortcut actionId="ToggleLineBreakpoint"/>.
-            System.out.println("i = " + i);
+public class Main {
+
+    public static void main(String[] args) {
+        CustomerDao customerDao = new CustomerDao();
+        VehicleDao vehicleDao = new VehicleDao();
+        RepairOrderDao repairOrderDao = new RepairOrderDao();
+
+        Customer max = customerDao.save(new Customer(null, "Max Mustermann", "max@example.com"));
+        Customer eva = customerDao.save(new Customer(null, "Eva Muster", "eva@example.com"));
+
+        Vehicle maxCar = vehicleDao.save(new Vehicle(null, max.id(), "VW", "Golf VIII"));
+        Vehicle evaCar = vehicleDao.save(new Vehicle(null, eva.id(), "BMW", "i3"));
+
+        repairOrderDao.save(new RepairOrder(null, maxCar.id(), "Inspektion & Ölwechsel"));
+        repairOrderDao.save(new RepairOrder(null, evaCar.id(), "Batterie prüfen"));
+
+        System.out.println("Kunden:");
+        customerDao.findAll()
+                .forEach(c -> System.out.printf("- #%d %s (%s)%n", c.id(), c.name(), c.email()));
+
+        System.out.println();
+        System.out.println("Fahrzeuge:");
+        vehicleDao.findAll()
+                .forEach(v -> System.out.printf("- #%d %s %s (Kunde #%d)%n", v.id(), v.manufacturer(), v.model(), v.customerId()));
+
+        System.out.println();
+        System.out.println("Aufträge:");
+        repairOrderDao.findAll()
+                .forEach(r -> System.out.printf("- #%d %s (Fahrzeug #%d)%n", r.id(), r.description(), r.vehicleId()));
+    }
+
+    interface Dao<T> {
+        T save(T entity);
+
+        Optional<T> findById(Integer id);
+
+        List<T> findAll();
+
+        void delete(Integer id);
+    }
+
+    static class CustomerDao implements Dao<Customer> {
+        private final Map<Integer, Customer> store = new LinkedHashMap<>();
+        private int nextId = 1;
+
+        @Override
+        public Customer save(Customer entity) {
+            int id = entity.id() == null ? nextId++ : entity.id();
+            Customer stored = new Customer(id, entity.name(), entity.email());
+            store.put(id, stored);
+            return stored;
+        }
+
+        @Override
+        public Optional<Customer> findById(Integer id) {
+            return Optional.ofNullable(store.get(id));
+        }
+
+        @Override
+        public List<Customer> findAll() {
+            return new ArrayList<>(store.values());
+        }
+
+        @Override
+        public void delete(Integer id) {
+            store.remove(id);
         }
     }
-}
\ No newline at end of file
+
+    static class VehicleDao implements Dao<Vehicle> {
+        private final Map<Integer, Vehicle> store = new LinkedHashMap<>();
+        private int nextId = 1;
+
+        @Override
+        public Vehicle save(Vehicle entity) {
+            int id = entity.id() == null ? nextId++ : entity.id();
+            Vehicle stored = new Vehicle(id, entity.customerId(), entity.manufacturer(), entity.model());
+            store.put(id, stored);
+            return stored;
+        }
+
+        @Override
+        public Optional<Vehicle> findById(Integer id) {
+            return Optional.ofNullable(store.get(id));
+        }
+
+        @Override
+        public List<Vehicle> findAll() {
+            return new ArrayList<>(store.values());
+        }
+
+        @Override
+        public void delete(Integer id) {
+            store.remove(id);
+        }
+    }
+
+    static class RepairOrderDao implements Dao<RepairOrder> {
+        private final Map<Integer, RepairOrder> store = new LinkedHashMap<>();
+        private int nextId = 1;
+
+        @Override
+        public RepairOrder save(RepairOrder entity) {
+            int id = entity.id() == null ? nextId++ : entity.id();
+            RepairOrder stored = new RepairOrder(id, entity.vehicleId(), entity.description());
+            store.put(id, stored);
+            return stored;
+        }
+
+        @Override
+        public Optional<RepairOrder> findById(Integer id) {
+            return Optional.ofNullable(store.get(id));
+        }
+
+        @Override
+        public List<RepairOrder> findAll() {
+            return new ArrayList<>(store.values());
+        }
+
+        @Override
+        public void delete(Integer id) {
+            store.remove(id);
+        }
+    }
+
+    record Customer(Integer id, String name, String email) {
+    }
+
+    record Vehicle(Integer id, Integer customerId, String manufacturer, String model) {
+    }
+
+    record RepairOrder(Integer id, Integer vehicleId, String description) {
+    }
+}