diff --git a/s1_a1_3_52.pdf b/s1_a1_3_52.pdf
index 3c4036d..f0e270e 100644
Binary files a/s1_a1_3_52.pdf and b/s1_a1_3_52.pdf differ
diff --git a/s1_a4.py b/s1_a4.py
index 246adbc..836500c 100644
--- a/s1_a4.py
+++ b/s1_a4.py
@@ -1,9 +1,15 @@
-i = 0
-s = 0.0
-while s <= 1.644934:
-    i = i + 1
-    s = s + 1.0 / (i * i)
-    print("Schritt: " + str(i) + ", Wert: " + str(s))
-
-
-#pi^2/6 = 1,644934, wird erreicht nach 14959887 Schritten
\ No newline at end of file
+#4.1
+import math
+
+z = ((math.pi**2)/6)
+x = "%(z).6f"%{'z':(math.pi**2)/6}
+y = 1.644934
+print(x)
+
+
+i = 1
+sum = 0
+while sum < y:
+    sum = sum + (1 / (i ** 2))
+    i = i + 1
+    print("Summe:", sum, ", Schritte: ", i) #Summe: 1.6449340000000012, Schritte: 14959887
diff --git a/s1_a51.py b/s1_a51.py
index bf77602..af3bcc9 100644
--- a/s1_a51.py
+++ b/s1_a51.py
@@ -1,19 +1,20 @@
-# 1a
-matrix_list = [[3, 0, -2, 11], [0, 0, 9, 0], [0, 7, 0, 0], [0, 0, 0, -3]]
-print(matrix_list)
-
-# 1b+c
-matrix_list_general = [[], [], [], []]
-MAX = 4
-for i in range(0, MAX):
-    print("Zeile " + str(i + 1))
-    for j in range(0, MAX):
-        n = int(input("Value:"))
-        matrix_list_general[i].insert(j, n)
-
-print(matrix_list_general)
-
-# 1d
-for i, row in enumerate(matrix_list_general):
-    for j, value in enumerate(row):
-        print(f'a[{i}][{j}] = {value} ')
\ No newline at end of file
+#5.1
+#a)
+matrix_list = [[3, 0, -2, 11], [0, 0, 9, 0], [0, 7, 0, 0], [0, 0, 0, -3]]
+print(matrix_list)
+
+#b+c)
+matrix_list_general = [[], [], [], []]
+MAX = 4
+for i in range(0, MAX):
+    print("Zeile " + str(i + 1))
+    for j in range(0, MAX):
+        n = int(input("Value:"))
+        matrix_list_general[i].insert(j, n)
+
+print(matrix_list_general)
+
+#d)
+for i, row in enumerate(matrix_list_general):
+    for j, value in enumerate(row):
+        print(f'a[{i}][{j}] = {value} ')
diff --git a/s1_a53_6.py b/s1_a53_6.py
index 3861705..b2fecbd 100644
--- a/s1_a53_6.py
+++ b/s1_a53_6.py
@@ -1,43 +1,52 @@
-#5_3
-list1 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
-print("start list", list1)
-
-a = list1[9]
-b = list1[8]
-c = list1[7]
-
-list1 = [c] + [b] + [a] + list1
-list1.pop(-1)
-list1.pop(-1)
-list1.pop(-1)
-
-print("new list", list1)
-print()
-print()
-
-#5_4
-#a
-word = "DONAUDAMPFSCHIFFAHRTSGESELLSCHAFTSSTEWARDESS"
-letters = list(word)
-print(letters)
-print("length:", len(letters))
-
-#b
-letters_once = []
-for element in letters:
-    if element not in letters_once:
-        letters_once.append(element)
-
-print(letters_once)
-print("length new:", len(letters_once))
-
-print()
-print()
-
-#5_5
-def sort(list2):
-    list2.sort(key = lambda x: x[1])
-    return list2
-
-list2 = [[1, 2, 3], [2, 1, 3], [4, 0, 1]]
-print(sort(list2))
\ No newline at end of file
+#5.3
+list1 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+print("start list: ", list1)
+
+list1.insert(0, list1.pop())
+list1.insert(0, list1.pop())
+list1.insert(0, list1.pop())
+
+print("new list: ", list1)
+print()
+print()
+
+#---------------------------------------------------------------------------------------------------------
+
+#5.4
+#a
+word = "DONAUDAMPFSCHIFFAHRTSGESELLSCHAFTSSTEWARDESS"
+letters = list(word)
+print(letters)
+print("length:", len(letters))
+
+#b
+letters_once = []
+for element in letters:
+    if element not in letters_once:
+        letters_once.append(element)
+
+print(letters_once)
+print("new length:", len(letters_once))
+
+print()
+print()
+
+#---------------------------------------------------------------------------------------------------------
+
+#5.5
+list2 = [[1, 2, 3], [2, 1, 3], [4, 0, 1]]
+print("List2 unsorted:", list2)
+list2.sort(key = lambda list2: list2[1])
+print("List2 sorted by 2nd value:", list2)
+print()
+print()
+#---------------------------------------------------------------------------------------------------------
+
+#5.6
+dict = { "Hund" : "wuff", "Katze" : "miau", "Kuh" : "muuh" }
+def function2(d, a):
+    print(a, ":", d[a])
+
+function2(dict, "Hund")
+function2(dict, "Katze")
+function2(dict, "Kuh")
diff --git a/s1_a61_2.py b/s1_a61_2.py
index 51b5784..f0da971 100644
--- a/s1_a61_2.py
+++ b/s1_a61_2.py
@@ -1,6 +1,10 @@
-string = "this is a test"
-replaced = string.replace(' ', '-')
-print(replaced)
-
-string2 = "hello, world"[-7::-1]
-print(string2)
\ No newline at end of file
+#6.
+s = "This is a test"
+print(s)
+
+#1.
+print("Spaces replaced with '-':", s.replace(' ', '-'))
+
+#2.
+s1 = "Hello, World"[-7::-1]
+print(s1)