\documentclass[a4paper,9pt]{scrartcl}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage{amssymb,amsmath}
\usepackage{geometry}
\geometry{a4paper,left=18mm,right=18mm, top=2cm, bottom=2cm}

\begin{document}
\section{braces}
\[-1+x ( x \big( 1+ x\Big(2 + x \bigg(3+ x\Bigg(4+x \Bigg) \bigg) \Big) \big) ) \]
\end{document}