diff --git a/s1_a4.py b/s1_a4.py
new file mode 100644
index 0000000..ca9f928
--- /dev/null
+++ b/s1_a4.py
@@ -0,0 +1,20 @@
+import math
+
+
+def is_equal_to_with_digits(expected, actual, digits):
+    return round(expected, digits) == round(actual, digits)
+
+
+expected_value = math.pi ** 2 / 6
+
+n = 1
+sum = 0
+
+while not is_equal_to_with_digits(expected_value, sum, 6):
+    sum += 1 / n ** 2
+    n += 1
+
+    if n % 100000 == 0:
+        print(n, round(sum, 6), round(expected_value, 6), expected_value - sum)
+
+print("result after", n, "iterations:", round(sum, 6), "; compare value:", round(expected_value, 6), expected_value - sum)
diff --git a/s1_a51.py b/s1_a51.py
new file mode 100644
index 0000000..b6d10e9
--- /dev/null
+++ b/s1_a51.py
@@ -0,0 +1,53 @@
+import numbers
+
+
+class BetterMatrix:
+    def __init__(self, matrix):
+        zero_count = 0
+        self.matrix = []
+        self.width = len(matrix)
+        self.height = len(matrix[0])
+
+        for row in matrix:
+            for col in row:
+                if col == 0:
+                    zero_count += 1
+                elif zero_count != 0:
+                    self.matrix.append([zero_count])
+                    self.matrix.append(col)
+                    zero_count = 0
+                else:
+                    self.matrix.append(col)
+
+        if zero_count != 0:
+            self.matrix.append([zero_count])
+
+        print(self.matrix)
+
+    def __getitem__(self, row):
+        if row > self.height or row < 0:
+            raise ValueError("Value must be between 0 and " + str(self.height - 1))
+
+        dest_array = []
+        dest_amount = (row + 1) * self.width
+        index = 0
+        while dest_amount > len(dest_array):
+            if isinstance(self.matrix[index], numbers.Number):
+                dest_array.append(self.matrix[index])
+            else:
+                for i in range(self.matrix[index][0]):
+                    if dest_amount > len(dest_array):
+                        dest_array.append(0)
+            index += 1
+
+        while len(dest_array) > self.width:
+            dest_array.pop(0)
+
+        return dest_array
+
+
+converted = BetterMatrix([[3, 0, -2, 11], [0, 0, 9, 0], [0, 7, 0, 0], [0, 0, 0, -3]])
+print(converted[0][0])
+print(converted[1][1])
+print(converted[2][2])
+print(converted[3][3])
diff --git a/s1_a52.pdf b/s1_a52.pdf
new file mode 100644
index 0000000..76caa18
Binary files /dev/null and b/s1_a52.pdf differ
diff --git a/s1_a53_6.py b/s1_a53_6.py
new file mode 100644
index 0000000..62fe5f5
--- /dev/null
+++ b/s1_a53_6.py
@@ -0,0 +1,33 @@
+print("Teilaufgabe 5.3")
+# Durch das Prinzip von Slicing und Verketten
+list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+newlist = list[7:] + list[:7]
+
+print(newlist)
+
+print("\nTeilaufgabe 5.4")
+long_word = "Donaudampfschiffahrtsgesellschaftsstewardess"
+
+char_array = [*long_word]
+print(char_array)
+print("Das Wort hat", len(char_array), "viele Buchstaben.")
+
+unique_characters = set(char_array)
+print(unique_characters)
+print("Das Wort hat", len(unique_characters), "eindeutige Buchstaben.")
+
+print("\nTeilaufgabe 5.5")
+list = [[1, 2, 3], [2, 1, 3], [4, 0, 1]]
+list.sort(key=lambda x: x[1])
+print(list)
+
+print("\nTeilaufgabe 5.6")
+
+
+def tiergeraeusch(tier):
+    return {"kuh": "muuh", "schwein": "oink", "pferd": "wieher"}[tier]
+
+
+print(tiergeraeusch("kuh"))
+print(tiergeraeusch("schwein"))
+print(tiergeraeusch("pferd"))
diff --git a/s1_a61_2.py b/s1_a61_2.py
new file mode 100644
index 0000000..c0c8b1f
--- /dev/null
+++ b/s1_a61_2.py
@@ -0,0 +1,21 @@
+print("Teilaufgabe 6.1")
+text = "This is a test"
+
+ergebnis_text = text.replace(" ", "-")
+print(ergebnis_text)
+
+print("\nTeilaufgabe 6.2")
+s1 = "Hello, World"
+
+s2 = s1[0:s1.find(" ")]
+
+# zwei alternative lösungen:
+# 1
+ergebnis_text = s2[::-1]
+print(ergebnis_text)
+
+# 2
+ergebnis_text = "".join(reversed(s2))
+print(ergebnis_text)
+
+s1 = ergebnis_text