diff --git a/src/main/java/tdd/setup/Calculator.java b/src/main/java/tdd/setup/Calculator.java
index 171f6d6..7c374ad 100644
--- a/src/main/java/tdd/setup/Calculator.java
+++ b/src/main/java/tdd/setup/Calculator.java
@@ -3,7 +3,7 @@
 // behaviour inspired by https://www.online-calculator.com/
 public class Calculator {
 
-    private String screen = "0";
+    private String screen = "";
 
     private double latestValue;
 
@@ -19,7 +19,7 @@ public void pressDigitKey(int digit) {
             screen = screen + digit;
         } else {
             latestValue = Double.parseDouble(screen);
-            screen = Integer.toString(digit);
+            screen = Integer.toString(digit); //Hier muss doch Double.toString(digit) stehen?
         }
     }
 
@@ -31,6 +31,7 @@ public void pressClearKey() {
 
     public void pressOperationKey(String operation)  {
         latestOperation = operation;
+        latestValue = 1;
     }
 
     public void pressDotKey() {
@@ -41,15 +42,18 @@ public void pressNegative() {
         screen = screen.startsWith("-") ? screen.substring(1) : "-" + screen;
     }
 
+
     public void pressEquals() {
         var result = switch(latestOperation) {
             case "+" -> latestValue + Double.parseDouble(screen);
             case "-" -> latestValue - Double.parseDouble(screen);
             case "x" -> latestValue * Double.parseDouble(screen);
             case "/" -> latestValue / Double.parseDouble(screen);
+            case "%" -> latestValue / 100;
             default -> throw new IllegalArgumentException();
         };
         screen = Double.toString(result);
         if(screen.endsWith(".0")) screen = screen.substring(0,screen.length()-2);
     }
+
 }
diff --git a/src/test/java/tdd/setup/CalculatorTest.java b/src/test/java/tdd/setup/CalculatorTest.java
index 3bf16e9..72f6951 100644
--- a/src/test/java/tdd/setup/CalculatorTest.java
+++ b/src/test/java/tdd/setup/CalculatorTest.java
@@ -16,4 +16,42 @@ void calculatorCanDoTwoPlusTwo() {
         calc.pressEquals();
         assertEquals("4", calc.readScreen());
     }
+
+
+    @Test
+    @DisplayName("should display result after dividing two positive numbers")
+    void calculatorCanDoEightDividedByFour() {
+        Calculator c1 = new Calculator();
+        c1.pressDigitKey(8);
+        c1.pressOperationKey("/");
+        c1.pressDigitKey(4);
+        c1.pressEquals();
+        assertEquals("2", c1.readScreen());
+    }
+
+    @Test
+    @DisplayName("should display a correct number with a dot") //Code von 2.2.8 auf 1.1+1.1 und davon auf 1.1
+    void calculatorCanAdditionWithTwoDots() {
+        Calculator c2 = new Calculator();
+        c2.pressDigitKey(1);
+        c2.pressDotKey();
+        c2.pressDigitKey(1);
+       /* c2.pressOperationKey("+");
+        c2.pressDigitKey(1);
+        c2.pressDotKey();
+        c2.pressDigitKey(1); */
+        assertEquals("1.1", c2.readScreen());
+
+    }
+
+        @Test
+        @DisplayName("should display result after pressing percentage")
+        void calculatorCanPercentage() {
+            Calculator c3 = new Calculator();
+            c3.pressDigitKey(1);
+            c3.pressOperationKey("%");
+            c3.pressEquals();
+            assertEquals("0.01", c3.readScreen());
+        }
+
 }