\documentclass{article}

\usepackage[margin=1cm]{geometry}
\usepackage{graphicx}
\usepackage{tabularx}

\begin{document}
\begin{tabularx}{\textwidth}{p{0.5\textwidth} p{0.5\textwidth}}
\includegraphics[keepaspectratio, width=.5\textwidth]{ha_frei_gutschein.png} & \includegraphics[keepaspectratio, width=.5\textwidth]{ha_frei_gutschein.png} \\
\includegraphics[keepaspectratio, width=.5\textwidth]{ha_frei_gutschein.png} & \includegraphics[keepaspectratio, width=.5\textwidth]{ha_frei_gutschein.png} \\
\end{tabularx}
\end{document}