diff --git a/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java b/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java
index aaef8862..0bcd0592 100644
--- a/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java
+++ b/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java
@@ -11,6 +11,7 @@ public class Calculator {
     private String screen = "0";
 
     private double latestValue;
+    private double latestLatestValue;
 
     private String latestOperation = "";
 
@@ -31,7 +32,7 @@ public String readScreen() {
     public void pressDigitKey(int digit) {
         if(digit > 9 || digit < 0) throw new IllegalArgumentException();
 
-        if(screen.equals("0") || latestValue == Double.parseDouble(screen)) screen = "";
+        if(screen.equals("0") || latestValue == Double.parseDouble(screen) /*|| latestValue == Double.parseDouble(screen) + 1*/) screen = "";
 
         screen = screen + digit;
     }
@@ -59,8 +60,18 @@ public void pressClearKey() {
      * auf dem Bildschirm angezeigt. Falls hierbei eine Division durch Null auftritt, wird "Error" angezeigt.
      * @param operation "+" für Addition, "-" für Substraktion, "x" für Multiplikation, "/" für Division
      */
+
     public void pressBinaryOperationKey(String operation)  {
+        if(!(latestValue ==0)) {
+            latestLatestValue = latestValue;
+        }
+
+        /*if(!latestOperation.equals("")) {
+            latestValue += Double.parseDouble(screen );
+        }
+        else {*/
         latestValue = Double.parseDouble(screen);
+        // }
         latestOperation = operation;
     }
 
@@ -118,7 +129,7 @@ public void pressNegativeKey() {
      */
     public void pressEqualsKey() {
         var result = switch(latestOperation) {
-            case "+" -> latestValue + Double.parseDouble(screen);
+            case "+" -> latestValue + Double.parseDouble(screen) + latestLatestValue;
             case "-" -> latestValue - Double.parseDouble(screen);
             case "x" -> latestValue * Double.parseDouble(screen);
             case "/" -> latestValue / Double.parseDouble(screen);
@@ -127,5 +138,6 @@ public void pressEqualsKey() {
         screen = Double.toString(result);
         if(screen.endsWith(".0")) screen = screen.substring(0,screen.length()-2);
         if(screen.contains(".") && screen.length() > 11) screen = screen.substring(0, 10);
+        if(screen.contains("Infinity")) screen = "Error";
     }
-}
+}
\ No newline at end of file
diff --git a/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java b/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
index addc5f26..5fbba088 100644
--- a/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
+++ b/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
@@ -41,5 +41,50 @@ void testSquareRoot() {
     }
 
     //TODO hier weitere Tests erstellen
-}
+    @Test
+    @DisplayName("should display 0.0 after pressing the clear key")
+    void testClearKey() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(3);
+        calc.pressBinaryOperationKey("+");
+        calc.pressDigitKey(7);
+        calc.pressDigitKey(1);
+        calc.pressClearKey();
+
+        String expected = "0";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+    @Test
+    @DisplayName("should display Error after pressing the equals key")
+    void testDivideThroughZero() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(3);
+        calc.pressBinaryOperationKey("/");
+        calc.pressDigitKey(0);
+        calc.pressEqualsKey();
+
+        String expected = "Error";
+        String actual = calc.readScreen();
 
+        assertEquals(expected, actual);
+    }
+    @Test
+    @DisplayName("should display 6 after adding 1, 2 and 3")
+    void testTwoOperations() {
+        Calculator calc = new Calculator();
+        calc.pressDigitKey(1);
+        calc.pressBinaryOperationKey("+");
+        calc.pressDigitKey(2);
+        calc.pressBinaryOperationKey("+");
+        calc.pressDigitKey(3);
+        calc.pressEqualsKey();
+
+        String expected = "6";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+
+}