\documentclass[11pt,a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage[ngerman]{babel}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{hhline}
\usepackage{courier}
\renewcommand{\baselinestretch}{1.5}
\usepackage[left=3cm,right=3cm,top=2.5cm,bottom=2cm]{geometry}

%Farbig
\usepackage[svgnames,table,hyperref]{xcolor}

\usepackage{pifont}
%zitieren
\usepackage[round]{natbib}
\bibliographystyle{plainnat}

% Tabellen
\usepackage{multirow} 
\usepackage{multicol} 
\usepackage{tabularx} 
\usepackage{longtable} 
\usepackage{array}


\usepackage{listings}

\lstset{ %
  language=R,                     
  basicstyle=\footnotesize\ttfamily,breaklines=true, 
  numbers=left,                   
  numberstyle=\tiny\color{gray},  
  stepnumber=1,                   
                                  
  numbersep=5pt,                  
  backgroundcolor=\color{Grey!5}, 
  showspaces=false,               
  showstringspaces=false,         
  showtabs=false,                 
   
  tabsize=2,                      
  captionpos=b,                   
  breaklines=true,                
  breakatwhitespace=false,        
  %title=\lstname,                 
                                  
  keywordstyle=\color{blue},      
  commentstyle=\color{Green},   
  stringstyle=\color{DarkGreen},      
  escapeinside={\%*}{*)},         
  morekeywords={*,...}            
  literate=%
    {Ö}{{\"O}}1
    {Ä}{{\"A}}1
    {Ü}{{\"U}}1
    {ß}{{\ss}}1
    {ü}{{\"u}}1
    {ä}{{\"a}}1
    {ö}{{\"o}}1
}

% Bilder
\usepackage{graphicx} 

%Titelseiten angaben
\author{Max Mustermann}
\title{Musterthema}
\date{Foo, der 42. Barte 1972}

% Angaben zu Kopf und Fußzeilen
\usepackage{fancyhdr}
\pagestyle{fancy}
\lhead{\slshape\rightmark}
\chead{}
\rhead{\slshape\leftmark}
\lfoot{}
\cfoot{\thepage}
\rfoot{}
\renewcommand{\headrulewidth}{0.4pt}
\renewcommand{\footrulewidth}{0pt}

\renewcommand{\baselinestretch}{1.5}\normalsize



\begin{document}