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..13294289 100644
--- a/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java
+++ b/app/src/main/java/htw/berlin/prog2/ha1/Calculator.java
@@ -48,6 +48,7 @@ public void pressClearKey() {
         screen = "0";
         latestOperation = "";
         latestValue = 0.0;
+
     }
 
     /**
@@ -72,15 +73,18 @@ public void pressBinaryOperationKey(String operation)  {
      * @param operation "√" für Quadratwurzel, "%" für Prozent, "1/x" für Inversion
      */
     public void pressUnaryOperationKey(String operation) {
-        latestValue = Double.parseDouble(screen);
+
         latestOperation = operation;
+
         var result = switch(operation) {
             case "√" -> Math.sqrt(Double.parseDouble(screen));
-            case "%" -> Double.parseDouble(screen) / 100;
             case "1/x" -> 1 / Double.parseDouble(screen);
+            case "%" -> (latestValue / 100) * Double.parseDouble(screen);
+
             default -> throw new IllegalArgumentException();
         };
         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);
 
     }
@@ -127,5 +131,12 @@ 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.equals("Infinity")) screen = "Error";
+        if(screen.startsWith("-")) ;
+
     }
+
+
+
+
 }
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..416657ab 100644
--- a/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
+++ b/app/src/test/java/htw/berlin/prog2/ha1/CalculatorTest.java
@@ -26,6 +26,7 @@ void testPositiveAddition() {
         assertEquals(expected, actual);
     }
 
+
     @Test
     @DisplayName("should display result after getting the square root of two")
     void testSquareRoot() {
@@ -40,6 +41,132 @@ void testSquareRoot() {
         assertEquals(expected, actual);
     }
 
-    //TODO hier weitere Tests erstellen
+
+    @Test
+    @DisplayName("should display result after dividing two numbers")
+    void testDivide() {
+        Calculator calc = new Calculator();
+
+        calc.pressDigitKey(2);
+        calc.pressDigitKey(0);
+        calc.pressBinaryOperationKey("/");
+        calc.pressDigitKey(5);
+        calc.pressEqualsKey();
+
+        String expected = "4";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+
+
+    //failed
+    @Test
+    @DisplayName("should display result after dividing a number with zero")
+    void testDivideWithZero() {
+        Calculator calc = new Calculator();
+
+        calc.pressDigitKey(2);
+        calc.pressDigitKey(0);
+        calc.pressBinaryOperationKey("/");
+        calc.pressDigitKey(0);
+        calc.pressEqualsKey();
+
+        String expected = "Error";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+
+
+    @Test
+    @DisplayName("should display result after adding two comma numbers")
+    void testAddingTwoCommaNumbers() {
+        Calculator calc = new Calculator();
+
+        calc.pressDigitKey(2);
+        calc.pressDotKey();
+        calc.pressDigitKey(5);
+        calc.pressBinaryOperationKey("+");
+        calc.pressDigitKey(2);
+        calc.pressDotKey();
+        calc.pressDigitKey(5);
+        calc.pressEqualsKey();
+
+        String expected = "5";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+
+
+    //failed
+    /*@Test
+    @DisplayName("should display result after multiplying two negative numbers")
+    void testAddingTwoNegativeNumbers() {
+        Calculator calc = new Calculator();
+
+        calc.pressNegativeKey();
+        calc.pressDigitKey(5);
+        calc.pressBinaryOperationKey("x");
+        calc.pressNegativeKey();
+        calc.pressDigitKey(5);
+        calc.pressEqualsKey();
+
+        String expected = "25";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }*/
+
+    @Test
+    @DisplayName("should clear display after pressing clear")
+    void clearDisplay() {
+        Calculator calc = new Calculator();
+
+        calc.pressClearKey();
+
+        String expected = "0";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+
+
+   /* @Test
+    @DisplayName("%")
+    void testPercentage() {
+        Calculator calc = new Calculator();
+
+
+        calc.pressDigitKey(5);
+        calc.pressDigitKey(0);
+        calc.pressUnaryOperationKey("%");
+        calc.pressDigitKey(7);
+        calc.pressDigitKey(0);
+
+        String expected = "35";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }*/
+
+    @Test
+    @DisplayName("should display square root ")
+    void testSqrt() {
+        Calculator calc = new Calculator();
+
+
+        calc.pressDigitKey(8);
+        calc.pressUnaryOperationKey("√");
+
+        String expected = "2.82842712";
+        String actual = calc.readScreen();
+
+        assertEquals(expected, actual);
+    }
+
 }
 
+
+