\documentclass[11pt, a4paper]{scrreprt}

% Prepare for german input, with english as an alternative
\usepackage[german,english]{babel}
\usepackage[latin1]{inputenc}

% Use T1-Encoding to allow proper hyphenation of words with umlauts
\usepackage[T1]{fontenc}
\usepackage{ae,aecompl} 

% For graphics, use \includegraphics from the graphicx package
\usepackage{graphicx}

% Insert URLs to websites using \url from hyperref
\usepackage{hyperref}

% Increased page size
\usepackage{a4wide}

% Useful mathematical packages
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{latexsym}

%
\pagestyle{headings}
%
%
%
\newcommand{\setEnglish}{
\selectlanguage{english}
\def\Chapter{Chapter}
\def\Section{Section}
\def\Theorem{Theorem}
\def\Proposition{Proposition}
\def\Lemma{Lemma}
\def\Corollary{Corollary}
\def\Definition{Definition}
\def\Remark{Remark}
\def\Example{Example}
\def\Examples{Examples}
\def\Consequence{Consequence}
\def\Fact{Fact}
\def\Notation{Notation}
\def\Conjecture{Conjecture}
\def\Exercise{Exercise}
\def\AExercise{Additionalexercise}
\def\Project{Project}
\def\Problem{Problem}
\def\Observation{Observation}
}

\newcommand{\setGerman}{
\selectlanguage{german}
\def\Chapter{Kapitel}
\def\Section{Abschnitt}
\def\Theorem{Satz}
\def\Proposition{Proposition}
\def\Lemma{Lemma}
\def\Corollary{Folgerung}
\def\Definition{Definition}
\def\Remark{Bemerkung}
\def\Example{Beispiel}
\def\Examples{Beispiele}
\def\Consequence{Folgerung}
\def\Fact{Tatsache}
\def\Notation{Schreibweise}
\def\Conjecture{Vermutung}
\def\Exercise{Aufgabe}
\def\AExercise{Zusatzaufgabe}
\def\Project{Projektaufgabe}
\def\Problem{Problem}
\def\Observation{Beobachtung}
}

%
%
\theoremstyle{break}
\newtheorem{theorem}{\Theorem}[section]
\newtheorem{proposition}[theorem]{\Proposition}
\newtheorem{lemma}[theorem]{\Lemma}
\newtheorem{corollary}[theorem]{\Corollary}
\newtheorem{consequence}[theorem]{\Consequence}
\newtheorem{conjecture}[theorem]{\Conjecture}
\newtheorem{fact}[theorem]{\Fact}
\newtheorem{observation}[theorem]{\Observation}

\theoremstyle{definition}
\newtheorem{notation}[theorem]{\Notation}
\newtheorem{definition}[theorem]{\Definition}
\newtheorem{convention}[theorem]{Convention}
\newtheorem{remark}[theorem]{\Remark}
\newtheorem{example}[theorem]{\Example}
\newtheorem{exercise}[theorem]{\Exercise}
\newtheorem{project}[theorem]{\Project}
\newtheorem{exercisestar}[theorem]{\AExercise}
\newtheorem{problem}[theorem]{\Problem}
\newtheorem{nothing}[theorem]{\negmedspace \negthinspace}
\newtheorem{examplestar}[theorem]{Example$^*$}

\theoremstyle{break}
\newtheorem{examples}[theorem]{\Examples}
\newtheorem{examplesstar}[theorem]{Examples$^*$}
\newtheorem{remark2}[theorem]{\Remark}

%

%
\renewcommand{\theenumi}{\roman{enumi}}
\renewcommand{\labelenumi}{\rm(\theenumi)}

\renewcommand{\theenumii}{\alph{enumii}}
\renewcommand{\labelenumii}{\rm(\theenumii)}

\numberwithin{equation}{section} 
%
\setlength{\unitlength}{1cm}
%

% Some useful commonly used macros

\newcommand{\N}{\ensuremath{\mathbb{N}}}    % Set of natural numbers - N
\newcommand{\Z}{\ensuremath{\mathbb{Z}}}    % Set of integers - Z
\newcommand{\Q}{\ensuremath{\mathbb{Q}}}    % Set of rational numbers - Q
\newcommand{\R}{\ensuremath{\mathbb{R}}}    % Set of real numbers - R
\newcommand{\C}{\ensuremath{\mathbb{C}}}    % Set of complex numbers - C
\newcommand{\F}{\ensuremath{\mathbb{F}}}    % Finite field
\newcommand{\K}{\ensuremath{\mathbb{K}}}    % Generic field

\newcommand{\ZmodZ}[1]{\ensuremath{\Z/#1\Z}}% Z mod nZ

\newcommand{\gen}[1]{\langle#1\rangle}      % "Generated by", "span of"
\newcommand{\abs}[1]{\lvert #1 \rvert}      % absolute value

% Math operators / functions should be declared as follows, if you want
% them to "look good":
\DeclareMathOperator{\proj}{proj}


\begin{document}

% Sprache waehlen
\setGerman
%\setEnglish

\chapter{*** Vortragstitel ***}

*** Name des Autors, Artikel ***

*** Name des Vortragenden, Datum ***

\section{Einleitung}

\begin{theorem}
Ein Satz: $a^2 + b^2 = c^2$.
\end{theorem}
\begin{proof}
Ein Beweis.
\end{proof}

\begin{equation}
\sum_{n=1}^{\infty} \frac{1}{n^2} = \frac{\pi^2}{6}
\end{equation}

\begin{thebibliography}{99}
\bibitem{Abramenko/Brown} Peter Abramenko, Kenneth S.\ Brown\footnote{Bibliothekslabel IMMER Name/Name:Jahr}, {\em Approaches to Buildings}, Springer, Berlin. Book in preparation.
\end{thebibliography}

\end{document}