diff --git a/src/main/java/tdd/setup/Calculator.java b/src/main/java/tdd/setup/Calculator.java
index 171f6d6..c4620aa 100644
--- a/src/main/java/tdd/setup/Calculator.java
+++ b/src/main/java/tdd/setup/Calculator.java
@@ -3,43 +3,75 @@
 // behaviour inspired by https://www.online-calculator.com/
 public class Calculator {
 
+    // Ausgabe auf dem Screen default auf 0
     private String screen = "0";
 
+    // letzter eingegebener Wert
     private double latestValue;
 
+    // letzte ausgewählte Operation
     private String latestOperation = "";
 
+
+
+    /**
+     * Method read Screen
+     * Methode gibt String value der Variablen Screen zurück
+     * @return screen
+     */
     public String readScreen() {
         return screen;
     }
+
+
+    /**
+     * Method pressDigitKey
+     * Method changed to Fix Multiplication of double digit values
+     * @param digit
+     */
     public void pressDigitKey(int digit) {
         if(digit > 9 || digit < 0) throw new IllegalArgumentException();
-
-        if(latestOperation.isEmpty()) {
-            screen = screen + digit;
-        } else {
-            latestValue = Double.parseDouble(screen);
-            screen = Integer.toString(digit);
-        }
+        Integer.toString(digit);
+        screen = screen + digit;
     }
 
+
+    // Noch nicht getestet
+    // Alle grauen Tests sind noch nicht getestet
     public void pressClearKey() {
-        screen = "0";
-        latestOperation = "";
-        latestValue = 0.0;
+        screen = "0";               // Ausgangszustand Screen (deault Zustand)
+        latestOperation = "";       // Default Zustand
+        latestValue = 0.0;          // Latest Value wird auf 0.0 gesetzt
     }
 
+    /**
+     * Method pressOperationKey
+     * Fix Multiplication of double digit value
+     * @param operation
+     */
     public void pressOperationKey(String operation)  {
         latestOperation = operation;
+        latestValue = Double.parseDouble(screen);
+        screen = "0";
     }
 
+
+    /**
+     * Method pressDotKey
+     * .contains(".) fix to ignore the input of multiple dots in one number
+     */
     public void pressDotKey() {
-        if(!screen.endsWith(".")) screen = screen + ".";
-    }
+        if(!screen.contains(".")) screen = screen + ".";
+    }   // Wenn Screen nicht mit . endet mach nen Punkt rein
+        // Wenn man Zahlen zwischen die Punkte schreibt kann man mehrere Punkte in eine Zahl machen
+
+
+
+    // Noch nicht getestet
+    public void pressNegative() { screen = screen.startsWith("-") ? screen.substring(1) : "-" + screen; }
+    // Wenn Screen mit - anfängt dann mach screen erster Platz im Index 1 (positiv/vorzeichnfrei)
+    // Wenn Screen nicht mit - anfängt dann mach "-" + screen (Minuszeichen wird gesetzt)
 
-    public void pressNegative() {
-        screen = screen.startsWith("-") ? screen.substring(1) : "-" + screen;
-    }
 
     public void pressEquals() {
         var result = switch(latestOperation) {
@@ -50,6 +82,17 @@ public void pressEquals() {
             default -> throw new IllegalArgumentException();
         };
         screen = Double.toString(result);
-        if(screen.endsWith(".0")) screen = screen.substring(0,screen.length()-2);
+        if(screen.endsWith(".0")) screen = screen.substring(0, screen.length()-2);
+
+
+        // if(screen.endsWith(".0")) screen = screen.substring(0,screen.length()-2);
     }
+
+    /**
+     * Davor Richtiges Verzeichnis in Ubuntu wählen
+     * git status
+     * git add .
+     * git commit -m 'Test Nachricht'
+     *
+     */
 }
diff --git a/src/test/java/tdd/setup/CalculatorTest.java b/src/test/java/tdd/setup/CalculatorTest.java
index 3bf16e9..3ce1c55 100644
--- a/src/test/java/tdd/setup/CalculatorTest.java
+++ b/src/test/java/tdd/setup/CalculatorTest.java
@@ -16,4 +16,66 @@ void calculatorCanDoTwoPlusTwo() {
         calc.pressEquals();
         assertEquals("4", calc.readScreen());
     }
+
+
+
+    /**
+     * 1. Grüner Test
+     * Press Negative Key
+     * -5 * 2 Ergebnis sollte - 100 sein
+     */
+    @Test
+    void calculatorCanDoMultiplicationWithNegativeNumbers () {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(5);
+        calc.pressNegative();
+        calc.pressOperationKey("x");
+        calc.pressDigitKey(2);
+        calc.pressEquals();
+        assertEquals("-10", calc.readScreen());
+    }
+
+
+    /**
+     * 1. Roter Test
+     * do multiplication with double digit numbers
+     * 20 * 50 = 1000
+     */
+    @Test
+    @DisplayName("Calculator displays correct result of the multiplication of two digit numbers!!")
+    void calcCanDoMultiplicationOfDoubleDigitNumbers() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(1);
+        calc.pressDigitKey(0);
+        calc.pressOperationKey("x");
+        calc.pressDigitKey(2);
+        calc.pressDigitKey(0);
+        calc.pressEquals();
+        assertEquals("200", calc.readScreen());
+    }
+
+
+    /**
+     * 2. Roter Test
+     * press Dot Key Multiple times
+     * Online Calculator ignores multiple dot inputs
+     */
+    @Test
+    @DisplayName("Calculator ignores input of multiple dots")
+    void calculatorIgnoresMultipleDotsInOneNumber () {
+        Calculator calc = new Calculator();
+        calc.pressDotKey();
+        calc.pressDigitKey(8);
+        calc.pressDotKey();
+        calc.pressDotKey();
+        calc.pressDigitKey(5);
+        assertEquals("0.85", calc.readScreen());
+    }
+
+
+
+
+
+
+
 }