Fix minor typos

Author: hw3456

2_Fundamentals.ipynb

@@ -2470,7 +2470,7 @@
    "source": [
     "#### Methods\n",
     "\n",
-    "Functions that are defined within a class are called it's methods. Methods may either only be called through a object or through the object and class (classmethod/staticmethod). Their first parameter is either a referene to the object, the class (classmethod), or neither (staticmethod). The reference to the object or class is passed automatically when the method is called; it does not have to be listed manually in the parameter list.\n",
+    "Functions that are defined within a class are called its methods. Methods may either only be called through a object or through the object and class (classmethod/staticmethod). Their first parameter is either a referene to the object, the class (classmethod), or neither (staticmethod). The reference to the object or class is passed automatically when the method is called; it does not have to be listed manually in the parameter list.\n",
     "\n",
     "Python Methods are virtual by default, i.e. methods of the same name of a base class are always overloaded (see [Vererbung](#Vererbung)). Therefore a method of a base class that calls another method defined in the same base class may end up calling a method of a derived class that overloads it (if called from a derived class)."
    ]

4_Pandas.ipynb

@@ -115,7 +115,7 @@
     "year_1990 = {'Germany':70000000, 'France': 50000000, 'Netherlands': 12000000}\n",
     "year_2021 = {'Germany':83000000, 'France': 67000000, 'Netherlands': 17000000, 'Greece': 13000000}\n",
     "\n",
-    "inhabitants_1990 = pd.Series(year1990) ##Konvertierung in Pandas-Series\n",
+    "inhabitants_1990 = pd.Series(year_1990) ##Konvertierung in Pandas-Series\n",
     "inhabitants_2021 = pd.Series(year_2021)\n",
     "\n",
     "print(\"Inhabitants in 1990:\")\n",