\documentclass[11pt]{article}
\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}
\usepackage[sfdefault]{biolinum}
\usepackage[a4paper]{geometry}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{amsmath}
\usepackage{thmtools}
\usepackage{mathrsfs}
\usepackage{mathtools}
\usepackage{tikz}
\usetikzlibrary{positioning,decorations.pathreplacing, cd, babel}

\tikzset{
every edge/.style = {draw, -to}
}

\biolinum

\theoremstyle{definition}
\newtheorem{definition}{Definition}[section]
\newtheorem{example}{Beispiel}[subsection]
\newtheorem{lemma}[subsection]{Lemma}

\newcommand{\ob}{\mathsf{ob}\text{ }}
\newcommand{\mor}[3]{\mathsf{Hom}_#1(#2,#3)}
\newcommand{\cat}[1]{\textnormal{\textsf{\textbf{#1}}}}

\begin{document}
\include{./chapters/deckblatt.tex}
\include{./chapters/motivation.tex}
\include{./chapters/Grundlagen.tex}
\include{./chapters/Kegel_und_Ko.tex}
\include{./chapters/nat_trafo.tex}
\end{document}